i need the sauce

No, the softness of her breasts had nothing to do with it. What happened in that scene is that Ryouta was supposedly killed by another player using remote mines, but managed to survive by diving through a trapdoor in the corner of the room. Both Himiko and the attacker assumed he died, so the attacker took Ryouta's weapons and attempted to use them to kill Himiko, but seeing as Ryouta didn't die, the attacker was never able to arm the bombs since their original owner was still alive.

I apologize if you're joking, in which case I now feel like a smartass.