@OmniscientRock
Yes, I get that, but for me, it's not the fact he lost his lifespan that is the problem (he could have only 2year to live I would be ok with it) but why he has to (the catgirl backstabbing)
I feel it could have been avoided with the 3 of them (the older woman with enough experience, the Mc with his cunning, and Lille with her fighting reflex), thus why I felt the development was forced by the author to get a little extra "Oh, no" from the readers.