Chaosking
it would be more easy for him to reveal to the girls he is sure love him the most at the moment about his bloodline, how it works and the information he has about some future danger or something. I'm sure they would understand once he reveals his life is in danger... from there he would have an easier way with all of them and he can slowly add the other pokemons... i don't know why would he put himself in such a situation. Most of them have bloodline and know about them so they can easily believe him
you're playing a dangerous game here writer man, with that many yandere in the harem it's really hard to keep up with it, and it can get off rail easily with a massive harem filled with monopolizing yanderes in it i really hope ye have a plan to manage this. the protag being unable to do anything against a super hyped-up half n' half dragon is ok and all, but if ye don't want a bad end then you have to do something about it, probably give austie a buff or smth