Boy/man supernatural ghost

From Liquid Passion:
The last thing Arata expected was for his cousin that he'd almost forgotten about to show up on his doorstep. But it soon becomes apparent that Kazuto is not what he appears to be.

Itsuki is a student 18 years of weak appearance, one day while walking down the street is surrounded by a band of criminals, Murashige Ryouta tries to save him but Itsuki is perfectly able to defend itself from the thugs because he practiced Aikidou (Art Japanese martial based on defense). Ryouta is impressed with the strength of Itsuki and follows him to the house of his family. Ryouta begins to have a great fascination with the Aikido but even more by Itsuki

Hirofumi returns home when his father dies. Will he meet his high school friend Jin who confessed to him when they were teenagers and was part of the reason Hirofumi hasn't returned home for 15 years?