pokemon tf story gym leader to powerhouse

koga had passed on the gym to janine but wasn’t sure if he wanted to keep up with the elite 4 job and wanted to be a posion type to help her without realising he found a bunch of weird looking sludge just outside of the gym when he went to pick it up his body changed into that of a venuasaur not realising his daughter janine was watching who than catches him and realises its a mega venasaur which gives her much more strength for the battle and koga forgets most of his past.