Nighttime for Just Us Two Vol. 3 (Kodansha, 2022)

After running away from home, Koga-kun and Miyako finally reveal their true feelings, and become an actual couple… or so they thought. Along comes another alien, here to take Chiro-chan home. Which actually causes Koga-kun to lose his memories! That went south real fast! Miyako's resolved to fight tooth and nail to ensure their happiness, but what will become of them?!