Bright and Cheery Amnesia
Other names: 愉快的失忆, 明るい記憶喪失, Akarui Kioku Soushitsu
Author: Oku Tamamushi
Artis: Oku Tamamushi
From Girls in Boxes: Mari's girlfriend, Arisa, loses her memories of the past three years, including all memory of their life together. However, it turns out that being crazy in love with someone transcends all realms of possibility.