Hm..... In that case, maybe he's a beautiful young man? Oh, or maybe a childish-looking trap! Half ghosts age much slower than humans, so it wouldn't be unlikely, right? Hehehe....
You had me at trap!Youki. You are amazing for planting that image in my head.
um...he have at least 300 "temporal" years. our Youmu have 60 (in PCB era) he have 5 times her age.Then, all depends of how we see Youmu: if she looks very young (like 10 years old, for example) he would have have a very handsome 50 years, but personally imagined who he even look more young (in his 40...maybe 30 :3) and only leaves his hair-beard-etc grow for look more old (and avoid discussions about be "not normal" same thing who happen with Rinnosuke)
...would be weird if Youki look only few years older than Youmu...and a trap! Youki would be funny, but random (maybe if we think who who he do that for look Youmu training without be discovered will make sense, but...)
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...i want my 30-40 years yummy handsome Youki! (biseinen, for contrast with our bishonen Rinnosuke) XD
very happy to see Youmu in a new game!
edit: i like the idea of a changeager Youki...his spirit is so iluminated who he can change his age if he wants....um interesting...interesting.