Then Ryuuroden will definitely satisfy you since it features, I think in all honesty, one of the most touching romantic stories I have ever read in a manga.
At first it really did seem like a cliche what's with all the childhood friends and stuff, but later volumes expand and expand and expand and expand upon the romance aspect so magnificently that the romance between the main hero and his fated love is so incredibly moving and touching, especially considering the various circumstances they were thrown into.
Touching and Deep is spot on for what I enjoy but most romance mangos are Tragic. Japan seem to love Tragic Dramas.
I'll say my favorite romance/relationship story in manga/anime is still
Chobits it may always be because of the lack of sex as the pay off so it retains an innocence and that huge challenge of accepting Chii as a partner/lover. Second for me would be
Ai Yori Aoshi would be number 1 if it was not a harem manga.
I read a bunch of things trying to find a good touching romance but all of them have lots of one sided fail to them which makes me hate the process of looking.
But to be honest I am a huge relationship junky and look for it in everything I read. Manga romances don't always work, and most manga genres like shounen mangas don't really focus on romance they tease at it (Hinata/Naruto) but they don't allow a pay off. So we have this Shippers Meme going around because of this.
My last historical fighting manga that I wished romance played a roll was
Vagabond there is a girl but dude has no desire for anything but his sword.
Everything else that touches on romance in Japanese Manga are romances between tragic characters that should not be, i.e. Incest, Teach/Student or something to that level where the story becomes dark or very depressing.
Romance of Three Kingdoms timelines seem to fall into the tragic love theme to me so I tend to avoid it.