MC probably got injected in the end of chapter 2 and that is how it happened... same injection that made Shion go crazy in the end of the chapter... doctor can reach all hospitals or have some very strong connections... that could be how also got to Rena when she visited the hospital after what she did in her old school... but... couldn't Ooishi-san see that? @_@ he is way too good to miss it... so the doctor most have been using connections and not going by himself... i legit think am solving the story from chapter 5... am so smart it's unreal V-V