A bored Rimuru Tempest accompanies Diablo when he goes to meet with an old friend in the Netherworld. What will happen when he meets an out-of-place human boy who piques his interest? (Tensei Shitara Slime Datta Ken and Mairimashita Iruma-kun crossover)

Two people forgotten by the world, finding comfort in each other and ultimately peace. But the newfound circumstances have brought that peace into question.