And no, they're not related, the dude isn't adopted, and the old guy isn't his stepfather either. This is just a oneshot based on another manga by Ogawa-sensei called "Boku no Papa ni Natte Kudasai" (Please Be My Daddy) which unfortunately has not been translated. The younger fellow Haruki is looked after one day after he passes out from exhaustion from work by the older man Katsumi. He's touched by Katsumi's kindess and ends up asking him to be his "papa" in order to make up for the absence of his own father in his childhood, and Katsumi agrees and they do a lot of cute father-son things together. Hopefully someone gets around to translating it.
And no, they're not related, the dude isn't adopted, and the old guy isn't his stepfather either. This is just a oneshot based on another manga by Ogawa-sensei called "Boku no Papa ni Natte Kudasai" (Please Be My Daddy) which unfortunately has not been translated. The younger fellow Haruki is looked after one day after he passes out from exhaustion from work by the older man Katsumi. He's touched by Katsumi's kindess and ends up asking him to be his "papa" in order to make up for the absence of his own father in his childhood, and Katsumi agrees and they do a lot of cute father-son things together. Hopefully someone gets around to translating it.