This is a collaboration that needs some context. So within the fishing industry of Japan, fishers organize themselves into Japan Fisheries Cooperatives (JF), and organizing the JFs is the National Federation of Fisheries Co-operative Associations (全国漁業協同組合連合会), also called simply JF Zengyoren (JF全漁連) in short. This national federation has a Seafood Promotion Committee (魚食普及推進委員) that, as the name suggests, promote the eating of fish and seafood in the country. We also have Sakana-kun (さかなクン), the boxfish-hat-wearing ichthyologist (= fish scientist) and mass media personality also having a hand in illustration, who frequently works with said committee in addition to other educational works on the varies life under the ocean. Click the above links to check out the related main sites.
Back to Taiko no Tatsujin after all these preface, with the release of Sakana-kun's new song Osakana Mainichi! Sakana-kun (おさかな毎日!さかなクン), the JF Zengyoren SPC negotiated collaborative efforts with the rhythm game franchise to include the song in an arcade version in the future. Playing the song also unlocks a collaborative outfit where a big-grinned Sakana-kun lies on Don-chan.
Speaking of fishing, did you know that Bandai Namco also has a running fishing simulator arcade game called Tsuri Spirits? Well, turns out it is also joining the collaborative efforts with both JF Zengyoren and Taiko no Tatsujin, making for a very fishy collab-triangle! Sakana-kun's new song will be added to Tsuri Spirits as one of the BGM tracks. Elements from Taiko and Tsuri Spirits will also be exchanged, including Don-chan being fishable from Tsuri Spirits for the campaign.
The above collaborations are slated to happen this summer, but with no set date as of now.
BNEI Press Release