Heat (MIYAMOTO Kano)

About a small agency “that does everything". The manager, Bun, has a very special tattoo and an affinity for smiling faces. Customers approach the manager with difficult problems and he solves them, with the fee for his services sometimes being paid with sex.

Miyamoto Kano's "Walker" universe timeline:
1) Are You Enemy?
2) Not/Love
-- Not/Love dj - The Reason Why We Live Together
-- Not/Love dj - Dog Days
-- Not/Love dj - Demonic Conversations
-- Not/Love dj - Brand New Lover
3) Heat (MIYAMOTO Kano)
-- Under the Skin
-- Lizards, Angels, and Daemons

The ones on ( -- ) are doujinshis. They give background or "add into" to some key points in the main story line. So you're not really missing anything even if you don't read it.