The most important thing with shows like I Told Sunset About You, is that the characters are relatable. No one wants to spend a couple hours watching a show with unrelatable characters and no violence.

Both Teh and Oh-aew have colourful, fleshed-out personalities, and are in situations many others are in, have been through, or will experience at some points in their lives. That helps bring the audience in and gives them that feeling of relatability.
Teh is ambitious and outgoing, it's obvious that he makes friends and conversation easy. However his actions are harsh and affect everyone around him.
Oh-aew, on the other hand, is reserved and observant so he tends to stick to people he knows and environments he knows, but is the most vibrant amongst his friends.

It's obvious that they're teenagers who do dumb things and make decisions that they'll look back on and cringe, and that's the most refreshing part about I Told Sunset About You, neither Teh or Oh-aew are perfect or smart about what to do, making them relatable.