Responses
I haven't read the other one, but I'd say it's not about that Tatsumi guy, but about how he gave up on love after his failed past relationship, five years ago, that obviously must have left him quite wounded, as he's still nursing a heartbreak: watching the obvious happiness of the people close to him probably reminds him of his own loneliness.
I'm a little surprised that this manga is based around Yura's unrequited love for Tatsumi. In the prequel, Yura was just a friend, and there was really no hint at all to his potential feelings for Tatsumi. The whole time he just seemed like a concerned friend.
Since his unrequited love is such a strong theme in this one, I would have expected it to be shown more prominently in the previous manga. Right now it just seems so out of nowhere. But maybe the mangaka wasn't originally planning the sequel.
Ah well. It'll still be good since I like this pairing.