He's geting old lol so he got white hair
Spoilers: (you have been warned)
From what I remember
The white hair J has is a result of the West Sea Rift (eroded dungeons) since he was there for 8 years, his hair turned white
Yes, this is what i remember too. After some time, everything inside the west sea rift becomes white (ashen).
Yes, but it's not the whole truth.
Spoiler, seriously.
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It's because he ate some of the corrupted monster meat. Luckily for him, it wasn't much and also because he's strong, so the corruption process is very slow. But steady.
his hair became white only after the time skip