Kiryuu Keiki gets to hang out with three cute girls in the Shodou Club (four if you count his imouto, which he doesn’t), but he wants a girlfriend. So imagine his shock when he finally receives a love letter from a secret admirer…along with a pair of underwear.
From there, Keiki tries to investigate which of the three girls (excluding his sister) could be the “Cinderella” to his Prince: the cool, mature senpai Sayuki (Taketatsu Ayana), the adorable blonde kohai Yuika (Hidaka Rina) or the approachable classmate Mao (Nomizu Iori).
In his interactions, the girls exhibit what could be construed as signals indicating they are the culprit, in addition to having feelings for Keiki beyond mere friendship, but nothing concrete until Sayuki happily accepts a date offer he accidentally makes when thinking out loud.
When he asks Sayuki straight up if “she has a secret” she’s not telling him about, she flees, and spends the entire next day at school very obviously avoiding him. Mao suggests he employ the “wall slam” tactic (much more effective in anime than IRL), which he does when he spots her walking home.
He tells her he knows her secret (assuming its the note and underwear); when she asks if that means he dislikes her now, he tells her it’s quite the opposite; after the initial shock, he was glad. Mind you, he makes no mention of what he’s talking about.
The next day, Keiki reports to the clubroom as requested, Sayuki makes him close his eyes, and when he opens them, she’s wearing a collar and leash, exposed her bra, and asking to be Keiki’s pet. That’s when Keiki knows he’s in for something a lot stranger than he bargained for!
Hensuki is another show that would probably benefit from being 12-13 minutes instead of double that; the “investigation” drags on too long even if it’s also meant to introduce the main players. While a decent-looking, this show is utterly by-the-numbers and generic except for the twist at the end, which doesn’t definitively answer the question of who gave him their underwear.
This will be the story of a guy whose female acquaintances each have their own unique kinks, which they’ll reveal to him because he’s a kind and understanding dude. It is notable that the show so far exhibits a particularly soft touch when it comes to its ecchi element. But where this goes from here—and whether and how the premise can be sustained for 12 episodes—very much remains to be seen.