"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 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.