While not around per se, there could be references to Ruroni Kenshin characters/events/techniques. Unless there was some Inuyasha crossing in there... 3x3 Eyes, and any number of other supernatural themed settings have ways to render a human protagonist ageless with greater or lesser degrees of limitation and drawbacks. In a mystical martial arts setting, it's perfectly in genre for a Master to live hundreds of years with little debilitation just through the power of their qi.
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows