‘Useless’ because IT JUST AIN’T WHAT IT IS.
I almost included this in my Ano Hana post, but ended up getting all SRS BSNS during it and, uh, didn’t. Which, ultimately, is probably a good thing, honestly!
Please keep in mind that this is all ass-hattery.
So, we could interpret Yukiatsu’s dressing up as Menma thing an attempt on his part to have her all for himself, particularly when taken in tandem with his encouragement of the others to forget about the poor girl. We could interpret it just straight-up as Yukiatsu being a total jerk who is trying to inflict greater pain on a former friend who is already clearly very damaged by the deaths of a friend and his mother in his childhood. We could interpret it as a sign that Yukiatsu is himself very disturbed. Or, the most likely of our options, as some combination of all three.
Or, y’know, we could go the fujoshi/fudanshi (it seems like I actually know more fudanshi than fujoshi these days!) and look at it through the lens of BL.
So. It is implied that Menma and Jintan both liked each other back in the day… “the day” in this case being “when Menma was still alive and Jintan wasn’t a shut-in”. In the present time, Yukiatsu acts arrogantly toward Jintan and dresses up as Menma. He also tries to avoid looking directly at Jintan, and just generally displays a distaste toward having to be around him at all.
OBVIOUSLY YUKIATSU WANTS JINTAN DUH!
Yukiatsu dresses up as Menma, the girl Jintan liked. Jintan used to be the outgoing group leader, but is now a “pathetic” social pariah who avoids as much contact with others as possible and never goes to school. Yukiatsu’s attitude toward Jintan could be borne out of a disappointment in him, a feeling that he has been weak by falling into his agoraphobic ways (actually, this part possibly holds true regardless of whether anything else I’m saying is of any substance whatsoever). Yukiatsu looked up to Jintan when they were a kid, so there’s a sense of betrayal in Jintan’s failure to overcome the deaths of both Menma and his mother. He’s supposed to be stronger than that.
Eh, yeah, so, Yukiatsu was hot for Jintan (well, y’know, the ten year old’s equivalent of “hot for”), Jintan liked Menma, and now Yukiatsu goes out in drag as Menma because he’s a jerk and is trying to hurt Jintan and also is trying to become Menma.
OR! Yukiatsu is trying to get Jintan to break from thinking he can see Menma – Yukiatsu thinks he’s just flat-out crazy and seeing things – in order to then be able to usurp what he believes to be Menma’s position in Jintan’s heart!
OR! Yukiatsu resents Jintan’s “betrayal” in large part because he had a crush on him and so feels that his own attraction to Jintan calls his strength of character into question because Jintan is weak!
HOLY FUCK MAD BL SKILLZ RIGHT THERE!
Oh, the fujoshi. She is so good at seeing BL in everything.