User blog comment:Martialmaniac/Ten - Is it worth mentioning?/@comment-48285-20180417181148/@comment-5780397-20180417213249

You make a point, I'll reword my fsecond question slightly.

It was actually stated several times that Ren is necessary to enter Greed Island: it's in the instruction manual, and we see Feitan and Gon using it to enter the game (the trigger is Hatsu, but, as the manual says, you use Ren to activate it, exactly like during the water divination test).