Combine water and powdered agar in a container, mixing well. Cover loosely with plastic wrap and microwave at 600W for 5 minutes.
2
Remove and stir thoroughly, then cover again and microwave at 600W for 1 minute until the agar becomes translucent.
3
Gradually add the red bean paste in about 4 portions, incorporating a small amount at a time while stirring and breaking up any lumps until fully combined.
4
Place the bowl over a larger bowl filled with cold water and let it cool for about 2 minutes.
5
Pour the mixture into narrow cylindrical molds and refrigerate for 2 hours until completely set.
6
Once set, open the top of the mold and gently push from the bottom to release the mizuyōkan. Serve as whole sticks or cut into bite-sized pieces.