Responses
not really, fortunately the author briefly explains anything related to Lover Boy when mentioned in this manhwa, and in my opinion, it doesn’t have much effect in Sparkling Baby since it is only used to explain why Hanjoon has “conflicts” with personal relationships, however it is not the main focus, just a character background.
if you feel curiosity about Jaeha and his relationship with Hanjoon then yeah! you should read it

Should i read 'lover boy' first to better understand the spin off story?