Black or White has an actor couple http://www.mangago.me/read-manga/black_or_white/
https://www.lezhin.com/ko/comic/scene untranslated but fits your description
This tag might be of better help http://www.mangago.me/tag/actors/
The first part of Momentum
Thank you both!!! <3
Momentum is great. Here are a few more I remembered
- My director http://www.mangago.me/read-manga/my_director/
- The Rain in Montecarlo http://www.mangago.me/read-manga/the_rain_in_montecarlo/
Also that Lezhin one has been translated now, it's called "Behind the scenes"
https://www.lezhin.com/en/comic/scene_en
Just search the relevant tags for greater choice though
BL/Shounen ai manga/webtoons where they have to be actors playing romance roles? Thanks!