adachi is not supposed to be a sexy character. his design is deliberately plain and uncharismatic; he's always rumpled, his clothes don't fit, his haircut is weird, and he's not especially handsome. he's not especially ugly, either, though, because the point of him is to fade into the background. he was designed to be unremarkable and not look especially suspicious!
regardless, as he is a bad guy, he's always had a good number of fans who think he's sexy! and some of those fans.... work for atlus, lol.
adachi gets sexier every time he appears in a spinoff, probably because the only reason he keeps being brought back in spinoffs and adaptations is fanservice for adachifuckers. i think this is very funny. please enjoy this little gallery depicting adachi's transformation over the years!
big shoutout to rokuro saito-sensei in particular, the artist who did the persona 4 arena ultimax manga, who is probably the horniest for adachi out of all official persona 4 artists!