They are basically fighting over who likes the nurse (the one that helped Subaru in the previous one) more, and that scary guy is saying in friendship, you gotta crack your stomachs like you crack your chopsticks... OKAY let me explain. There is a saying in Japan that goes like: "Hara (=stomach) wo Waru (=crack)" which means "no secrets, let it all out" kinda thing. "Waru" is the verb for crack, and it can also mean when you split the chopsticks apart. .......I'm sorry I'm terrible at explaining this, but the CM itself is cute! I can't wait for a Shota version!