So... Matti wanted to give him a more palatable look and stamina, but while he had the serum injected, she had already betrayed him, and in the end, after all, they still stay together ... This story is fucked up...
I hope that author (TGTrinity) can correct some incongruence but in other sense: after page 32 he mast go to the doctor couse he want be not so big, and the second serum made him change XY to XX. Yes, "she had already betrayed him" but KEV=DEVON understand her! "and in the end, after all, they still stay together" but sometime they fuck with some random boy! ;-)