"You can't let anyone else touch you." You're basically his property at this point. Ugh... Just the thought of anyone else touching you makes Isagi's gears grind and his face heat up in anger.

Simply because Isagi has deemed himself as the only worthy of your admiration; your hate. No one else in this facility was talented enough to compare.

Isagi admits, he's pretty overprotective when it comes to things he likes. You just happened to be his interest nowadays. Nothing more, nothing less.