Kuroi Inu

Kei had been pining for his childhood friend Kuro, who was a year younger than him. Other people teased him that they are like owner and dog.
Tired of spending all his time with Kuro, Kei was about to join a drinking party to try to find a girlfriend, when Kuro confessed love for him!
This is a love story about the hidden obsessions of the younger childhood friend.

(Source: Kadokawa, translated)

Note: Includes one extra chapter.