Not Enough Time(2005)

Yousuke suddenly shows up on the door step of his old classmate Tanigawa, with whom he lost touch after high school. While the two had a budding relationship back in school, things fell apart and they decided to part ways and search for their true love. However, it might be that their relationship in the golden days of high school was what they have been looking for all along. Can they both figure out the meaning of true love that they never knew back then?

Life is like a cycle and so is love. What once was lost can turn full circle and be found once more. Shoko Hidaka's collection of eye-opening love stories also includes a coffee store owner that has to choose between his work and his love for an aspiring artist, and a public prosecutor who must hide his personal relationship with a detective from their working peers.

(Source: Juné)

A second storyline involves Shibuya and Mikami, two of Tanigawa's students and a misunderstanding that threatens their relationship.
The story between Shibuya and Mikami continues at one of the chapters of Signal.

Includes:

1) Signs of Emotions

2) Not Enough Time (spin-off of "Signs of Emotions")

3) Complicated and Easy

4) Right or Left

5) Long Distance Relationship

6) Stay (continuation of "Not Enough Time")