That is actually pretty neat and mysterious. Maybe in the revisited version there might by more to Nanafuse which could be absolutely amazing. So far in my time playing I have encountered him 4 time, each time confusing me a lot. Lol
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Despite the question already being answered. Yeah, in the original, he's just a spirit given form by Shun and a name by Hiroyuki. And depending on who you go with during the test of courage, he'll either pop up as their old teacher Botan, show up once as Kounosuke, or show a glimpse of himself for a short few seconds. The problem is he's not meant to be recognized for exactly what he is.
If you do, he'll stop you and complete wipe all memory of him from you. But he will always show up when you least expect him.
If they do more to add to him, i'd be glad to see it. The only instances I've ever seen him play a deeper part is once during Juuichi's route and multiple times for Kounosuke's. But we'll have to wait and see what the creators do with him here.