While "bear" is a pretty good substitute for "gachimuchi", I sometimes see "hard gay" interchangeably used. It's a kinda specific Japanese BL term...
Aahh, he's having a friendly chat with a ninja!That ninja won't do!!How vexing!!And just like I thought, he turned out to be a hard gay!Aaah, isn't that Shiba over there!?Kyaaa!! Shiiiiba ♥That hard gay... Someday, I'll assassinate him!!ShibaWahahahahaha!