Gundham Tanaka had been in bed sick for two days,though no one knew.Of course there was one other person knew,Teruteru Hanamura.Of course he knew,he was the reason Gundham was sick.He had given the breeder food poisoning so  he could get away with what he was planning to do without him finding out.

Either...

He was planning to Kill Sonia,the only other person who could get between Teruteru and Gundham.

Or

He was planning to Kill Kazuichi after he called Gundham something that he thought crossed the line.(Either a LGBT Slur,witch i must ask you to sensor if you do or just something really insulting.))

After Teruteru hid the body he desided to go to Gundham's dorm and make sure that no one could hurt him or get between them ever again.