It's implied that he was, at least partially, responsible for Maya's decent into delinquency. While Maya's parents were divorcing (he would have been 15-16 at the time) he introduced Maya to the university party scene. This included things like booze, smoking, casual sex, and clubs. The impression I get, though it's never explicitly stated, is that his bullying was part egging Maya on, part embarrassing Maya, and part showing him up (so he wouldn't look good in front of Akira). Maya, whose world was being rocked, clung to *an* adult who was willing to pay attention to him. The result was the Maya seen in the first chapter.
Granted, it's not all Shimakawa's fault. A lot of that was Maya himself. Still, I can't help but think he wouldn't have been such a terrible person if Akira had been stable enough himself to be Maya's role model himself.
thax (=・ω・=)
You're very welcome!
just wondering ┑(￣Д ￣)┍ what exactly did shimakawa do to maya? they never really explain the details