I'm looking for a good work, preferably one with a sweet romance, where the hero suffers from some manner of severe heart condition. Preferably not one of those "he won't live to be X" ones, which I've seen rather frequently. Frankly, those are overdramatic, excessively heavy, and ignore the broad range of conditions that are far more treatable, and can be managed well enough to create no impact at all on one's lifespan. There are plenty of people whose conditions leave them plenty strong and active, and healthy, only they can't push too hard or too long. As minor as this sounds, there's plenty of conflict and internal pain involved, including the knowledge that many dreams simply won't ever come true, the inability to participate in some activities that had been fun until the condition was discovered, activities that one's friends still love, and possibly some major problems with fear and anxiety. There's plenty of room for conflict here, both on the side of the character who has to deal with all the things he can't do and on the side of friends/love interests who may be concerned that they might hurt the hero or frustration over the limits to what they can do.

I know there's a category for heart conditions, but a lot are a little short or even lacking in the description department, and I don't want to get invested in one of those ticking clock stories. Thus, I'm looking for advice on good manga/anime with a hero who has a heart condition that limits (maybe severely) some of his activity without making him legitimately weak or tired or guaranteeing a young death.