Responses
At the point the story is currently at, it has hinted that a second person likes Jinho, but in chapters 9 and 10 of "Stop at the Red Light" it shows that Jinho and Hwanung ended up together. In the latest chapter of "See You at the Crosswalk" it looks like Jinho is falling for Hwanung, so I'm thinking that it just ends up being unrequited love for the poor second guy. So, I guess it is kind-of a love triangle, but it hasn't really had that classic bitter-sweet feeling so far.
This author wrote another manga that focuses on Hae-in's partner, Jinho. It's called "See You at the Crosswalk;" it's on Lezhin: https://www.lezhin.com/en/comic/crosswalk_en. I like it so far; his partner is pretty cute. :)