He gave Karen the Goblin Slayer blade (essentially a weapon made to kill specific race, the other two of its kind are Demon and Dragon ones)
And after Karen saw how MC's little chuuni act looked a LOT like the old demon lord, and even knowing that if she fail to kill him, she'll probably ends up basically brainwashed like the guy he just use it on.
Then she noted that he seem to have gotten even stronger, or rather, even the skills he obtain seem to be higher grades too.
And upon realizing that from now on, the goblins under him will probably keep getting stronger, and with each passing their skills to him, Akira will keep getting even stronger.
She decide this might be her only chance to stop the potential threat.
And that night go visit him in just her underwear :v
:v sadly it looks like it's bi-weekly so next chapter won't be out until near the end of Sept.