Mahiro and the Sticker Collection

Mahiro and the Sticker Collection (まひろとシール集め, Mahiro To Shīru Atsume) is Chapter 46 of Onimai: I'm Now Your Sister!. It was originally published on Pixiv on November 28, 2020.

Summary
Mahiro and her friends get into the new sticker collecting fad.

Plot
At Mihari's university, her faculty advisor Chitose Azuma, who is revealed to have also been the doctor that examined Mahiro for her school physical, comments that Mihari is working hard. Mihari is happy to see her.

Chitose says that she is very pleased with Mihari's report, and notes that her brother's progress is quite promising, a compliment that Mihari thanks her for. Chitose says that good students get stickers, much to Mihari's confusion. Chitose puts a sticker, that contains her face and the work "GOOD", on Mihari's lab coat. Mihari asks her what this is supposed to be, and Chitose explains that she made some stickers in her spare time. Mihari thinks to herself how wierd Chitose is.

At school, Momiji tells Mahiro that she can have some sticker sheets. Mahiro is confused, and Momiji explains that she was sorting through her desk at home and found a bunch of unused ones. She says that she was super into stickers in elementary school, and this is what she has left. Miyo notes that there are so cute and reveals that she had a sticker book as well. Mahiro thinks to herself that girls love collecting stickers. Asahi says that she still collects them, which Mahiro isn't surprised about at all. Asahi explains that she collects the "bread stickers", causing Mahiro and Momiji to smile and note that that figures.

Momiji tells Mahiro that she's not going to use them, so she can have them if she wants. Mahiro doesn't know what to say, but hears Nayuta mention stickers. When Mahiro turns around, Nayuta quickly covers her mouth. Mahiro asks Nayuta if she likes stickers, but Nayuta tries to deny it. Mahiro asks Momiji if she minds if she splits them up, and Momiji says that she doesn't mind.

Mahiro gives one of the sticker sheets to Nayuta, making her happy. Mahiro notes that this is such an honest delight, and Asahi decides to give her some too. Asahi gives Nayuta one of her bread stickers, causing Nayuta to beam. Mahiro is amazed that she likes that too. Momiji decides that now she's happy too, and Miyo suggests giving her some stickers as well, both of their maternal instincts having kicked in.

Mai and Miyako notice that the girls appear to be having a sticker exchange party, with Mai noting that she was so into that way back when. Miyako asks if they should relive old times and bring in their old collections, which Mai says sounds fun. All the other girls get excited, and with that a new fad is born.

At home, Mahiro sits on the couch and notes that she has a bunch of stickers, but wonders what to do now. Mihari takes a peek and notes that one is cute, but asks Mahiro if she's a little old for sticker collecting. Mahiro insists that she's just going along with it just to be polite, and asks what you're supposed to do with a sticker collection anyway. Mihari says that she could put them in her planner, or in letter to friends. She mentions though that your favorites go into a sticker book for safekeeping, saying that she had one as a kid too. Mahiro is surprised and asks Mihari if she can see hers. Mihari looks through a cabinet wondering where it is, thinking that it might be in her room. She finds it, and notes that it really takes her back.

Mihari demonstrates that its got special paper for easy affixing and removal. Mahiro understands and asks to have it. Mihari is surprised, but after a moment of thought snatches it back and refuses saying that it has too many memories for her to part with it. Mahiro apologizes, and asks Mihari if she has any unused stickers she doesn't want, as she wants it to be an actual exchange.

Mihari begins to look though her drawer, then remembers the sticker that Chitose gave her and gives it to Mahiro. Mahiro asks who the person in on the sticker, and Mihari explains that it is her sensei from the lab at school. She says that Chitose gave her a good evaluation and a sticker, leading Mahiro to also think of her as creepy. Mahiro gets the feeling that she's seen Chitose before, likely at school, but Mihari says that she doesn't think that the two have ever met. Mahiro ultimately declines the sticker, saying that she doesn't want to have to explain it all, which Mihari figures.

Mihari says that the only other ones she has are practical use stickers, which Mahiro agrees to since stickers should be used. They turn out to be warning stickers warning about danger, poison, and radiation. Mahiro is surprised about these being for practical use, and Mihari explains that they are for labeling things in the lab. Mahiro yells at Mihari to stop working with such dangerous things, but Mahiri laughs and says that she was just kidding.

At school, Momiji and Nayuta think that the stickers Mihari gave Mahiro are so cool, and Mahiro thinks how glad she is that they're the right age for these. Mai and Miyako ask to see the stickers, despite Mahiro's protests. Miyako declares that its so lame that its cool again. Mahiro is flabbergasted, and notes that she'll never understand middle school sensibilities.

Nayuta comes up to Mahiro's desk and says that she wants to pay her back as well. Mahiro tells her that she doesn't have to, especially from her own collection, but Nayuta insists that trading them is the best part. She says that her "onee-san" gave her a bunch of a certain one, which leaves Mahiro confused. It turns out to be the same sticker that Chitose gave Mahiro, leading Mahiro to wonder what it going on.

When Nayuta gets home, Chitose is equally shocked to see that she got a radioactive warning sticker from Mahiro as part of the trade, wondering where it came from.

Characters

 * Mahiro Oyama
 * Mihari Oyama
 * Momiji Hozuki
 * Asahi Ōka
 * Miyo Murosaki
 * Nayuta Tenkawa
 * Chitose Azuma
 * Mai
 * Miyako

Trivia

 * Mihari's faculty advisor Chitose Azuma is revealed to be the doctor that examined Mahiro for her school physical without Mihari's knowledge in "Mahiro and the School Physical".
 * As mentioned by the chapter, in Japan, an annual contest of the Yamazaki Bread Company involves exchanging proofs-of-purchase stickers for dish sets.