I Was Dismissed from the Hero’s Party Because They Don’t Need My Training Skills, so I Strengthen My [Fief] Which I Got as a Replacement for My Retirement Money. Chapter 5 Discussion

Really like the premise, different from other "kicked out of the hero party" theme, this one focused on the realistic side. This one does not antagonizing the hero, rather explaining the problem of how dangerous it is if the MC continue adventuring with the Hero party as the danger level of the future quests would just making him killed instead if he continue adventuring with them.