I wanted to believe that maybe this dude had some real and cute feelings for our MC and was just dating similar girls to him so their friendship wouldn't be ruined, but the more scenes I see between them, it just looks like a depressing relationship.
He obviously doesn't care much about Sungwha's feelings but somehow the little he does care is enough to make Sangwha's unhealthy behavior to grow. Sanghwa has a big part of responsibility in this and it's not that the friend is the worst, but there's a lot of unbalanced power in their relationship that it's unhealthy.
The friend just wants to control him and keeping him at his service at any time. A friend wouldn't be treated as a maid, worker, pet, or slave, that ain't cute. Any relationship must be reciprocal and that's why Geum+Sangwha's relationship feels wholesome and BFF+Sangwha feels rotten.