Japan Post's Shikoku branch announced a Niyodo River frame-stamp sheet on 14 October 2026. Titled NIYODO BLUE!, the issue goes on sale on 19 October, with 800 sheets available.

The sheet contains ten 110-yen stamps and costs 1,800 yen including tax. Sales are planned at 228 post offices: all participating offices in Kochi Prefecture, together with the central post offices in Tokushima, Takamatsu and Matsuyama. Contracted postal agencies are excluded.

The official sheet illustration presents river scenery, including waterfalls, clear water, surrounding landscapes and flowers. Its photographic credit names Nobuyuki Takahashi. Online sales are scheduled to begin at 00:15 on 25 October, Japanese time, with shipping charges additional to the sheet price.

A presentation ceremony is scheduled for 13:30 on 19 October at the Niyodo Blue Tourism Council in Sakawa, Kochi Prefecture. Council representative Tetsuo Ohara and photographer Nobuyuki Takahashi are named as recipients.