Kawashima/Heberu Yumiko

"“Oh. Wait. I’ve been so wrong. If nobody observes an action being done, it can be argued that action was never done in the first place. Only when you perceive the action or its direct aftermath is it registered into public consciousness. Like, if a woodpecker made a tree fall somewhere in the provincial interior, might as well not exist until somebody notices it. Won’t exist if that one person stops thinking about it in all practical senses. Since nobody is listening to Susan’s ramblings, those ramblings were never registered in their minds, they never existed. But everything has an intrinsic right to exist! The act of ignoring somebody’s hard work is actively slaying said work out of existence! It’s cruelty! And Susan can’t confirm her own existence, because knowing you exist is simply self-perception; if you don’t rely on others to confirm your existence, then you’re everything and if you’re everything it’s the same as being nothing! It’s so simple! It’s like that schrodinger’s cat experiment where a cat locked in a poison-filled box can only be confirmed either dead or alive upon observation. A human not acknowledged by another sentient being or not being actively thought about just doesn’t exist! So, as not to waste the effort Susan put into creating her rants, Emily is listening to them! Emily Baker and currently myself is the only one making sure Susan Edwards exists! You’re not born with the right to exist! You have to earn it through your creations! Dang… You could make a manga about this. I mean… are we… could we be… No, forget it. To exist is the ultimate mercy: A mercy I don’t deserve, but one I wish to give out now.”"-Yumiko on what it means to exist.

Yumiko Heberu (Real name: Kawashima Yumiko) is one of the secondary protagonists of the manga One Neo Eon by Alpha Yu. The leader of the Robotics Club, she actually knows very little of robotics and is typically reserved and cold. However, this is later revealed to be a front, for she believes that if she cares too much about others, she will be guilty of burdening them. Indeed, Yumiko holds the belief that she does not deserve good things due to her criminal past in which she assisted Yamoto Daisuke and Ko Long in the creation of the Hunters. Eventually, despite doing much to help her friends, Yumiko gives into repressed suicidal urges and tricks herself into believing that she sacrificed her life for the greater good to atone for her crimes when in fact she needlessly and selfishly committed a suicide bombing that ultimately became a major factor in Eon realizing the negative impact of Unintentional Creation.

History
Born December 3rd, 2003 to a broken family in Japan, Kawashima Yumiko grew up in the Shibuya District, although as a child she frequently visited Harajuku and gained a passing interest in home-made clothes. However, at home, she was frequently abused by her mother. Gaining solace with her sister, Kawashima Hanako; Yumiko was able to find some peace in life. She saw school as a bore and frequently resented the fact that, in her words, "weirdos kept dreaming about (her)". It is during this time that Yumiko picked up playing the piano and would become prodigiously good at it, earning herself a reputation. It is also during this time that Yumiko became a delinquent and joined a small gang of youth, becoming a smoker and turning to violence, growing skilled in combat with a metal bat.

Eventually, this small gang was subcontracted by the Siblings of Death in order to serve as manual labour in creating the Hunters. It is during this time that Commander Emily Baker finds her and singles her out as the "Sacrifice" that will be used by Yamoto's Faction in order to destabilize Eon's mentality and soften him up to the idea of eventually becoming the god of the world. Yumiko began spying on Yamoto and Ko Long's meetings, where she learned on Code 95-E. Unbeknownst to her, she was allowed to do this. Eventually, this grew too much for Yumiko and the weight of her actions dawned on her, causing her to flee her criminal lifestyle.

Eventually, after Hanako tragically passed away, Yumiko was sent to live with her father, who had immigrated to Vancouver, Canada. This was actually carefully planned by Yamoto's Faction. However, Yumiko could not contain her urge to fall into delinquency and eventually began a life of smoking, drinking, and partying. This abruptly ended when she was sent into shock after seeing one of her parties turning into a chainsaw massacre. The trauma of this event sent her into despondency until she met a boy who would eventually befriend her. The two began dating. To mark a change in her character, Yumiko took on a new last name, Heberu, a Japanese transliteration of the biblical concept of Hevel.

This only continued to negatively affect Yumiko, as after she became friends with Susan Edwards and Emily Baker, she would feel that these blessings were undeserved and she was yet to atone for the lifestyle she had run away from. Curiously, even though Susan is the most proactive member of the Robotics Club, due to being barred from making clubs thanks to her edgy Anarcho-Marxist ramblings. Thus, she gave Yumiko the responsibilty of forming the Robotics Club with the school, also making her the de-facto leader. By night, Yumiko was always restless, trying to track down any Hunters in Richmond. She eventually found one and realized too late that it was stalking Eon. She saved Eon from it but the guilt caught up to her and she couldn't help but flee from her obligations. This painted a target on her back and eventually she was hospitalized by the Hunter. After her recovery, she was even more set in her belief that she didn't deserve good things. Eventually, even as she began teaching Eon how to create by showing him her book, Stockholm; and her music, the suicidal urges brought about by Yumiko's extreme inability to believe in herself proved too much, and during another encounter with the Hunter, Yumiko needlessly sacrificed herself, detonating the flare inside her hairpin right as the Hunter fired its gun, creating an explosion that destroyed them both.

Visions of Yumiko created by the god of the world would also commit suicide by detonating the flare inside her mouth and through her brain when realizing that Alpha Yu was a terrible mangaka. Even after this, more visions of Yumiko would look back upon their predecessor's deaths and remark that the tragedy of her own character was that in reality, people don't have clear-cut character arcs and frequently act out of selfishness, dying for no apparent reason. Ironically, this is of course a manga character talking about real life vs the conventions of manga.

Relationships
Yumiko and Hanako had an extremely close bond.

Yumiko is in the Robotics Club with fellow members Susan Edwards and Emily Baker, whom she is initially cold to.

Yumiko is enemies with the Hunter and is a target of Yamoto's Faction. She was formerly employed by Ko Long and the Siblings of Death.

Yumiko grows in respect for Eon and Multis as the series goes.

Yumiko is dating some mysterious entity.

Meta Commentary
Curiously enough, Yumiko appears to be in a committed relationship with an individual first described by Susan Edwards as extremely similar to Alpha Yu himself. This is eventually revealed in all but name to be Alpha Yu, which at first was a meta-joke but eventually evolved to be a commentary on the nature of the series and its relation to creation as it was also revealed in all but name that Alpha Yu was in fact not an author easter egg but rather an alternate persona within the world of One Neo Eon living one plane of existence above the characters as the god of the world. Funnily enough, both characters would end up killing themselves to make a point by the end of the story. (In fact, Yumiko has committed suicide twice successfully as shown in the main dimension and the road to the pocket dimension made by the god of the world for Eon to go through.

Shonen Bag Manga
Yumiko stars in many Shonen Bag properties outside of One Neo Eon. For example, she very clearly is the same person as the character Faithful from Run: The Pilgrim's Progress, a Shonen Bag adaptation of a classic novel. She can also be briefly glimpsed as a background character in the cover for Alpha Yu's light novel, Split Miracle. Additionally, Yu has gone so far as to make an image of her smiling as his profile picture on all of his social media accounts and frequently posts pictures of Yumiko to his instagram account. Additionally, in Laws of Nature, Yumiko is seen as a background extra. Due to this, it is also likely only a matter of time before she appears in Penguins: Defenders of Antarctica, if she has not already.

This makes Mastermind & Ice and Scales (released as a bundle under the title "I hate my work and why you should too!"), Moe Mecha Massacre, and Hellfire Dishwasher the only Shonen Bag manga to not feature Yumiko, the former due to it predating Yumiko's inception and the latter likely due to their short length.

Sunnny Rain/Waifu Under Indifferent Sun
Yumiko played a major role in the Animated MV Short "Sunny Rain", which was apparently based on a true story. In Sunny Rain, Yu is depicted as lonely and downtrodden until turning to a dakimakura and waifu ASMR, from which he constructs the persona of Yumiko, who then proceeds to uplift him after he reaches an emotional low point, helping him to find value in and love himself. The treatment of the video makes it appear factual, although it is important to remember that if this is the case, as a firsthand account it is embedded with extreme bias. Elements of Sunny Rain such as Yumiko's connection of Waifu ASMR can likely be seen as true for four reasons:


 * 1) Shonen Bag is extremely active in the Waifu ASMR community
 * 2) One Neo Eon's female cast is made almost entirely of Waifu ASMRtists that Shonen Bag has connections with
 * 3) The phrase "Addicted to Waifu ASMR" shows prominently on @shonen_bag on Instagram.
 * 4) Things done by Yumiko in Sunny Rain are almost word-for-word the recontextualized scripts of two existing ASMR audio roleplays.

Sexuality
This story was repeated in more detail in the 2021 manga "Waifu Under Indifferent Sun" where it was revealed that that itteration of Yumiko was intersex. However, as the two Yumikos are not strictly the same being (existing in two different levels of reality), it cannot be said that information about the Yumiko in one manga translates into another.