Scarlet

From Blissful Sin:

1-2) Scarlet
College student Akio is dating his beautiful classmate, Ryou. Unable to stand the slightest loneliness, Ryou accepts any girl who approaches him. One day, Ryou introduces Akio to a girl he is thinking of marrying which makes Akio decide to completely break it off with Ryou. Instead, a heart wrenching love story takes stage!

3-4) One Night Stand
During the day Harumi is just a normal businessman but when night comes he changes into a different person.

5) My Lover
Keito wonders why he is still in a relationship with the overly depressive Naoki