Kinoshita Hideyoshi at Swimming Pool (drawn by me)

(from [link])
Being a identical twin, Hideyoshi looks like Yuuko. The only difference in their appearance is their hairstyle (which doesn't count against their similar looks). If you had noticed, you can see that Hideyoshi is slightly taller than her. Hideyoshi is one of the rarely found people with ordinary minds in Class F, but because of that got often pressured by classmates. According to the twin's grandpa's words, Hideyoshi is owner of an unbelievable beauty, so much that Hideyoshi is often called a girl. Hideyoshi's loveliness even got nominated in the list of 'Guys who would look good in girl's outfit' sponsored by the Journalism club, but was dropped from the ranking after all, 'unfair' being the reason. At the end even girls come to forget his real gender.

As a result of Hideyoshi's friends (both male and female) wanting Hideyoshi to change (into sports clothes, etc.) in the girls changing room while Hideyoshi doesn't, Hideyoshi ends up changes separately altogether. For example, in case of a training camp (for the safety of his own and the others) Hideyoshi is given a private separate dressing room and bathroom. Throughout the school, there is even a rumor that Hideyoshi is actually of the 3rd gender, dubbed "Hideyoshi" (This could be just a joke) In Akihisa's case, Hideyoshi's photos are secretly sold and bought in the school's black market--the price of his photo being 5 times higher than photos of Akihisa in girl outfits. The only person who recognized him as a guy upon sight was Akihisa's sister, at which Hideyoshi was delighted (but only because Akihisa's sister didnt believe that Akihisa could be friends with girls). Hideyoshi also seems to blush embarrasedly sometimes when called a girl, but it may be something the animators throw in once in a while to make Hideyoshi look even more like a female.

Hideyoshi takes part in the Drama club, and specialize in vocal mimicry--be that a girl's or a boy's voice. Even though in many cases Hideyoshi is not too willing to act, once the situation starts Hideyoshi perfectly deals with the given role, thanks to the excessive drama spirit. Part of the reason why Hideyoshi is in Class F is because Hideyoshi got too absorbed into drama and couldn't keep up the grades. It seems Hideyoshi is especially weak in Classic Literature, which is an irony in its own right considering how Hideyoshi is always using the classic form of the Japanese language to converse with everybody.

In contrast to Hideyoshi lovely outlook belies an extremely strong stomach('Steel Stomach' as called by himself) that can even take in a potato seed. However even such stomach cannot stand against Mizuki's mighty lunch. Also, Hideyoshi's strength is higher than Akihisa which is seen when the former completely arm-lock the later rather easily when they're listening to his confession to Minami. Ironically, Akihisa thought he couldn't lose to Hideyoshi in terms of strength.

A running gag is that Hideyoshi chest is always covered with something usually to make the viewer think that his gender is ambigious or that Hideyoshi may have "breasts"(since in the anime female characters' breast is always covered by something). Though in season 2 episode 7 shows Hideyoshi with a male chest, not female one.h owever, in season 2 episode 1, the lifeguard who saw Hideyoshi bare chested on the beach did not believe Hideyoshi to be a boy.