Following the non-credit OP animation clip, Toho Animation's official YouTube channel has posted a short version promotional video for the OP theme song for the One Week Friends TV anime, "Niji no Kakera" (A piece of the rainbow) sung by 22-year-old Natsumi Kon. The song written/composed by Ai Kawashima will be released as her 3rd single in Japan on May 21.
Originally, Kon is a stage actress who has mainly performed in musical plays such as Romeo and Juliet as Juliet in 2011, Hamlet as Ophelia in 2012, and Les Misérables as Éponine in 2013. Then she released her 1st solo single "Watashi wa Souzousuru" (Majestic Prince 1st OP) in April 2013. She also made a gust voice appearance as a GDF public-relations officer named Kon Natsumi in the anime.
"Niji no Kakera" short PV
Natsumi Kon © Toho Entertainment
The CD jacket
15-second TV CM
(C)ONE WEEK FRIENDS Project
(C)MATCHA HAZUKI/SQUARE ENIX