Satsuki Complex - Vol. 2 Ch. 20

[MangaDex]

 

[Aleph0]

Well I'm pretty sure the brother must have first-hand knowledge of Satsuki's gender, isn't it common in Japan to bathe with family members until a certain age?

 

[tomatou_]

You are correct, Kouta says in volume 1 that he's sure Satsuki is a boy for that exact reason; they took baths together as kids. But what if Kouta is in on the conspiracy!? As the reader you have to rely on what everyone around Satsuki says, making it the perfect opportunity for a conspiracy theory! "That's ridiculous," you say? Where's your definitive iron-clad proof then?