Alchemy was a disproven science even by your era. That you're clearly from another world does support the idea of of other ones existing, of the Shinigami being pulled from his, and that this is potentially another one altogether. But, he was allegedly able to travel between ours and his before this. You, me, and the others would normally leave "other worlds" to the realms of fiction.

[So he says while trying to straighten out the clothing he admittedly isn't very fond of. Unlike L, he tucks his shirt in, then nods to the door behind him, past the sinks with the note.]

It urges against getting in without some code, but only mentions breaking down the door as a potential hazard.