This is not gender bender (at least not in any sense of "body changing," so not the tag here). It's a "girl was raised as a guy but then her secret gets out (to her cousin)" story. The MC's cousin is a physical girl who was raised as a guy and is famous as bishounen male idol. However, her body has always been female and in this comic at least she mostly identifies as female (who has had her secret discovered) even though the way she was raised and is famous as a guy makes it difficult for her to completely think of herself as female. The MC didn't even realize that his cousin was female (they didn't take baths or anything together) until during the events of this comic.

So maybe sort of gender bender in a "changing gender identity" way, but the tag definition specifically mentions body changing.

Base +5, amers +6, machine010 +5, olboiye +7, zykyne +7, justforehreader +5, map131313 +7

Really good artwork here, and an interesting story to boot. Can't wait for the virgin-taking scene.

Base +6

Is this story going to be "I thought you were a dude! That's why I ripped your towel away from you and grabbed your crouch!" ?

Base +6, ArnasB +7, draconian196 +10

Very nice!

Base +6

>lets his cousin into his apartment
>plays an AV on TV immediately
>jacks off in front of his cousin

Not sure if completely frank or completely not caring of how others think.
Or maybe it's just because "they're both guys, so it's okay".

Unfortunately, it didn't turn out that way...

Base +7, draconian196 +10, kaitouyami +6

这剧情，真稳

Base +6