the official s2 start is 66 like bee's said. but the older brother comes back into the story and has important character beats starting chpt 45 (of s1). yeonwoo also has some important moments that directly lead into events of s2. there's several scenes repeated in s2 from s1 that are shown from a diff pov (in this case yeonwoo's). so assuming u havent read s1 in its entirety already. i would highly recommend that u start from chpt 45 not from 66.
ohh lmao. my bad well then i was assuming u were another person hoping to skip right into s2 but in fact it was the opposite! i would say def read s2 but wait until its mostly or all completed so u get the full story. i also enjoyed BS s1 way more when i could read it all together rather than week to week. just my suggestion tho. s1 stands fine on its own wrt the first couple and where we leave off with them.
if u mean the other main character in season 2. that's Yeonwoo. and he wasnt with Taehwan but you will see in S2 that they have a "history" that neither has told anyone else about. its not a romantic history but i wont go into details (and imo u should avoid this comment section cause its FULL of spoilers omg). but he and taehwan did used to know each other and yeonwoo was present in s1. but only in a handful of chpts up until the final stretch of s1 (those last 10 chpts that are building up to s2) where yeonwoo appears alot more. in s2 we see some of the same events from s1 repeated but now from Yeonwoo's pov. so far the story is mainly from Yeonwoo's pov in s2 but gradually we get more insight into taehwan's mindset over time. tho not yet in the english chpts alas. hope this helps!
Can someone tell me what chapter started the season with the brother