I read this novel quite a long time ago and and can't remember the title. Hopefully you guys can help me find it. I read a lot of quick quick transmigration so it might got mix up with other novel. I can't remember much but if I'm not mistaken the MC travel trough various world to fulfill the wish of the miserable(?) cannon fodder/side character, then MC get to live as the cannon fodder/side character. I'm not sure is this is the main mission of MC or the other way around but I think the other mission is to make sure heroine/villain do their "role" or to help them be happy, something like that. What I can sur remember is that in one of the world MC travel the FL is an actress that has illness that when you reach age 30 you might die. The MC is a doctor/scientist that research on the illness. I think both their birthday date is same or close to eachother. I don't remember how the FL start to like MC, but because of her illness, FL don't want to confess to MC until she turn 30. FL afraid that she might die when she turn 30. MC on the other hand was busy researching about the disease, and want to give cure to the FL as a gift for her birthday. What she didn't tell FL that she also has the same illness. So when they turn 30 FL survive while MC not. As for the research, i think MC manage to find the cause of the problem, but didn't have enough time to prove it. I hope that could help and sorry for the broken grammar. English is not my first language