Context: Marutamachi Chika 丸太町ちか supports her friend's lesbian romance.
{Maru-chan φ kaiteru} hon mobarakayuriya mon na マルちゃん描いてる本もバラかユリやもんな [Well,] the books [that] {Maru-chan draws} is bara or yuri too, right?
ya mon - same as da mono だもの, used to give a reason for something, in this case, it makes sense for Maru, who draws lesbian fiction, to be supportive of lesbian romance.
autodoa de barasu na-- アウトドアでばらすなーー Don't [tell everyone] outdoors!!
