Shall I Write Your Love Letter?

Story

Employee-of-the-Month champion and service-industry all-rounder Lim Seongshik thought he’d seen everything, until he wakes up inside a bleak BL novel as none other than Elliot Brown, a minor villain doomed to die. In the original story, everyone meets their end at the hands of the protagonist, Arzen Theron. So Elliot decides to keep his past life as a writer hidden, lie low, and quietly avoid the one event that triggers the tragedy: ghost-writing a love letter. But life—and his cat—have other plans. A desperate situation forces him into becoming Arzen’s personal bed attendant, of all things.

Synopsis via AniList (English).