There is no official "Arino Games" download store. Your best bet is hunting down physical DS copies or playing fan-translated ROMs of the Japanese originals (at your own legal risk).
Here’s a clear and helpful text for the subject : Subject: Arino Games Download – How to Find & Play Kachou’s Classics arino games download
If you’re looking to download games featuring (known from the Japanese show GameCenter CX ), there are a few key titles to know. Arino is not the creator of the games, but the star of retro-challenge based games released by Bandai Namco and others. There is no official "Arino Games" download store
For retro gaming fans, the real fun is playing the actual Famicom/NES games Arino tackles – those are widely available on Nintendo Switch Online or legal emulation compilations. Arino is not the creator of the games,