If you're here and haven't watched Saezuru Tori wa Habatakanai: The Clouds Gather, go watch that first.
Story: This is a spin-off of the film mentioned above and follows Yashiro's best friend (and initial love interest) and his growing affection for Kuga (aka "Mad Dog"). Story is pretty loose here too, a classic standoffish MC and flirty love interest that end up getting close. It's a bit more passionate and sexual than the initial film due to both characters, uh, being able to do it I guess is the best way of putting it.
Characters: The MC, Kageyama, is a doctor who swears that he's straight but ends up subconsciously crushing on Kuga, a yakuza potential member who has been in the eye of Kageyama's friend's yakuza group. And they end up getting it on, of course.
Style: Same as the initial film, got that BL style. Kuga's art is quite nice, I like those sorts of character designs - edgy bad boy kinda thing.
Recommendation: I'd recommend it if you've watched Saezuru Tori wa Habatakanai: The Clouds Gather as it is a bit more sexual than that, I guess? But since it's an OVA special, don't expect to be getting the same kind of content.