Does anyone know what chapter did Jin appeared before the back story?

I can't recall any other chapters right now, but he has an important scene in chapter 21(〜￣△￣)〜

That's it! that's what I'm looking for, thank you very much it's a really great help ⊂((・▽・))⊃

Now I remember how horrible Jin is specially when it comes to grey's,
I'm tempted to ship them but then again I felt I'm forgetting something crucial.

he has appeared in chapter 50