Phones do come with email addresses, and that's primarily used instead of text messages, but there is SMS/MMS (at least, I'm pretty sure that's what Softbank's

Phones do come with email addresses, and that's primarily used instead of text messages, but there is SMS/MMS (at least, I'm pretty sure that's what Softbank's S!Mail is, though, I get the impression it's mostly just used in-network, by people on family plans). Also, Naver's 'Line' is particularly popular for messaging right now.