Yeah I think it's from when she got him to put on that wig for Comiket or whatever and then he and Narumi took a selfie: http://www.mangago.me/read-manga/it_s_difficult_to_love_an_otaku/nbt/32518fab88b99fa2/Vol1_Ch51/3/
So cute, eh? (▰˘◡˘▰)
Actually you're right that it IS Hanako, but she's NOT crossplaying: http://www.mangago.me/read-manga/it_s_difficult_to_love_an_otaku/nbt/c405574f80994d11/Vol1_Ch2/18/
Oh, crap. I messed up. This is Hirotaka http://www.mangago.me/read-manga/it_s_difficult_to_love_an_otaku/nbt/32518fab88b99fa2/Vol1_Ch51/3/
The very last page wtf!!! Lollolo "Cuz I got a gurl too" while she slowly undid her hair..... Ahhhh that was great