Chateu

Does anyone know the title of this manga where it’s isekai (i think). MC doesnt age and wears black to ‘mourn’ for someone and he has to guard this princess and reclaim her throne. The princess dreams of MC’s early childhood days (some type of super power) and is in love with him but shes like underage.

It’s one the early mangas that was isekai before the isekai concept became popularized