For reference, this (well, the original version with the oni) is the story recounted by Subaru to Ram.
The Gambier Who Cried
Don't cry."So I'm leaving, back to the distant Abyss. Goodbye. Try not to get lost, okay. I'll still be your friend, no matter where I might be."
...so said the letter left behind by Lifebuoy-kun. Parody of The Red Ogre Who Cried, a children picture book story."Dearest Gamby, please get along with the shipgirls, and live happily with them. If I continue to stay with you, they might think you're still a bad Abyssal."So saaad!