Sun Moon Radiant Bureau
This sounds a lot like I Have 48 a Day which is a great novel. Same premise of mc and other characters being able to transmigrate into different story worlds and having to complete certain tasks. If you haven’t read I Have 48 Hours a Day yet, then go read it. One thing I liked was the nonexistent nationalism. Like how the author wasn’t furiously spamming ‘China #1, Japan bad’ when the mc went into a story world based in Japan. Now this is sounding quite like a promotion for I Have 48 Hours a Day, but I swear it’s not. It’s just a novel that I highly recommend you check out. I swear this is not a promotion.