File:Omaru Polka and Momosuzu Nene in summer time by Kou Mashiro.jpg

Summary
Full image and many images in Kou's new sketchbook "Polka Sketchbook 2": https://twitter.com/itsuwa0815/status/1550737493112553473

Source: https://twitter.com/itsuwa0815/status/1553343545045843968