Combatants Will Be Dispatched!, Vol. 9 (manga)

Thanks to humanity’s greatest mind, Lilith the Black, and her hypersonic anti-submarine depth charge, the pesky exploding hideout problem is fifinally resolved!
Now that the Grace Branch is up and running again, it won’t be long before Lilith can return to Earth… and she intends to bring Six with her?! But fifirst, the group takes on one last job investigating the recently uncovered ruins with the help of someone they haven’t seen in a while: Patrasche Rose.