Deaikei (出会い系) means something "for an encounter" in Japanese.
Deai kissa (出会い喫茶) are coffee shops where men look at girls through a one way mirror and try to start the date if they like the girl.
Deaikei saito (出会い系サイト) refers to online dating websites.
Some kissa have been raided because of anti-prostitution laws.
References
Deai-kei Wikipedia(Text) CC BY-SA