Long story short, ever since Nova became 1st in command, there's always been some type of rivalry.. Mayu also thinks Nova is trying to brainwash mirae 😇 and since she's such a GOOD friend she tries to eliminate Nova (for a temporary while, they can't really die unless their vital organs are damaged) but for Nova, he just likes to piss off Mayu just for fun, no real motive. But this makes Mayu hate him more so oops