20 SEIKI SHOUNEN: UJIKO UJIO SAKUHINSHUU

Two manga artists are trying their best to have their work accepted by someone who appears to be their superior. However their latest work has been denied and their superior requests that they should write a manga about a drama where a man protects the peace of the world. The two get together and begin to write a manga about a boy who promises a girl protection! — Description from AniList community (anilist.co).