When a Man Loves a Man (1 Volume)
Story of several guys working in host clubs.
Professional rivalry, mistaken identities, unrequited love, and jealousy test Shinkawa's and Takaaki's friendship on a semi-regular basis. But when Iwaki Kyousuke, Takaaki's old flame and mentor, returns to seduce Shinkawa away to a new host club, will Takaaki be able to persuade Shinkawa to stay, or will his devotion to Iwaki cause him to lose Shinkawa's partnership? (taken from Obsession)

Last Waltz (2 Volumes)
At the end of When a Man Loves a Man, Shinkawa had rejected Iwaki's invitation to become the number one host at his new club. But now the rivalry between Schnapps and the Rusty Nail is heating up.

Irokoi (3 Volumes)
Follows the star-crossed love relationships of four hosts, Takaaki, Iwaki, Shinkawa and Kenzaki. Interesting story and well-developed characters, but you should probably read the preceeding three When a Man Loves a Man series to understand the backstory.

U:V (2 Volumes)
The final arc of the series on the four hosts and their relationship. Iwaki introduced his nephew, Ozaki Kazuomi, to both Takaaki and Shinkawa; Takaaki is to train Kazuomi before being passed over to Shinkawa. However, Shinkawa still has doubts about Takaaki's feelings for Iwaki; has Takaaki really put his feelings for Iwaki behind him? What about Kenzaki, who has such love and passion for Shinkawa that he's willing to do anything for him?