Inside the Tentacle Cave manga volume 4 features story by Umetane and art by Abi.

Our heroines think they have dealt with The Black Ooze once and for all, reducing it to ashes deep within the lascivious cave where it dwells. But the Ooze is smarter than it seems, sending tendrils below the kingdom's sewers, feasting—and growing stronger and larger—on bodily fluids and waste, quietly biding its time for the perfect opportunity to strike.

That time is now. Caught unawares, our heroines fall and the city now lies in ruins. The last line of defense is Queen Letitia, who just might be powerful enough to repel The Black Ooze. But will her hubris cost her her kingdom?