Frank and Leo became really good friends after the war. It had started out with Hazel forcing them to spend some time together, but, they'd eventually realized that they both liked Mythomagic.
The two of them would get together in Bunker Nine, and play for hours. Nico joined them occasionally (which Leo thought Hazel may be responsible for.) Whenever the three of them had tournaments, it would result in yelling, death threats, and really, really, bad puns.