[ryuurui]

sorry i added some more info to my post.

you sure there is no other seal under the 石川 one on the first picture?
you won't be able to determine an artist without his pen name, and that should be revealed by the seal below the first one. His sig reads 石川 and some flip flop that could be 書　(written by), which is usually used on calligraphy under the sig, but it does not look like 書 in cursive or any other script to me.