The Hitman's Regret

Novice hitman Sig works together with his partner Naoe to carry out assassinations.
To Sig, Naoe is everything -- someone to look up to, a teacher, and even a lover.
But one day, Sig's inexperience costs him a shot at their target. And he feels horribly about it.
Still, however, Naoe has no choice but to punish him in the most erotic way imaginable.

This work takes place a bit after "How to Seduce a Hitman".
There's a story summary on the first page, so you might be able to enjoy this without reading the rest of the series... maybe...

Features a happy ending with plenty of love, but it's a little harsh.
- Crossdressing
- Colon teasing
- Vomiting
- Squirting
- Cum-in-eye
- 1 cover
- 40 pages