Looking for new romance manga with a touch of showbiz and school life in it. I really liked this one that had a guy like this girl and that girl's sister is in showbusiness with him so I'm looking for the name of that one too but I welcome any new showbusiness romance manga!

I'm not really into that genre but I found Cross Account acceptable.
You haven't really specified what type of "Showbiz"/what part of it you're into.(TV/radio/games/idols...)

If you add horror I also have others in mind but I don't think you're looking for that.
BTW.:most Korean manhwa artists are obsessed with idols ,social media and money, so if you want to try almost any of them set in the present, they usually contain some elements of showbiz. (At least for me it's annoying since they idealise the industry too much).

(Almost all Korean action Novel MC's sister fall in that category so it's even a bit of a cliche.In some cases they end up dragging the story into that terrain). 😢