a girl with a schoolbag stands beside a public toilet whth a piece of paper which said'prohibition of use'(sorry,my english is poor)
scatbooru is the only website about omorashi i can
log in in my country

consider using a VPN/proxy to get past your country's restrictions.

I do not know the image you talk about sorry.
With a proxy like www.croxyproxy.com you can try other sites like:
chan.sankakucomplex.com
rule34.xxx/index.php?page=post&s=list&tags=all
gelbooru.com/index.php?page=post&s=list&tags=all
e-hentai.org
www.pixiv.net/en (you need to make a free account for this one to view 18+ things)

Good luck!