Artist. Apparently he has another pen-name and circle, but does not want the relation between two names to become public.
Nickname: ysmmzr
The other name: やしま (Yashima)
Circle name: MEGADEATH
https://www.pixiv.net/users/399426
https://www.pixiv.net/users/16312149
https://www.pixiv.net/stacc/ltdh
https://www.pixiv.net/stacc/ysmmzr
https://twitter.com/vanadium_w
https://twitter.com/ysmmzr
https://twitter.com/intent/user?user_id=44062517
https://twitter.com/intent/user?user_id=840313199815671808
https://sketch.pixiv.net/@ysmmzr
https://skeb.jp/@vanadium_w
https://ysmmzr.tumblr.com
http://ysmblg.blogspot.com
http://twitpic.com/photos/ysmmzr