Natsume Yujinchou: Tamayura no Ie

On a hot day at the end of summer, Natsume receives an “invitation” addressed to his grandmother Reiko, delivered from the shadows while walking home. Though unsure how to respond, he heads out river fishing with Nishimura and the others, only for Nyanko-sensei to suddenly appear there...!?

(Source: Hakusensha, translated)