Rehydrate the dried hijiki seaweed.

Drain the rehydrated hijiki seaweed thoroughly.

Mix the drained hijiki seaweed with mentsuyu sauce.

Microwave the hijiki mixture at 500w for 30 seconds.

Remove the pit from the umeboshi plum and shred the plum flesh.

In a bowl, combine the cooked rice, hijiki mixture, shio-konbu, and shredded umeboshi plum.

Mix all the ingredients well until evenly distributed.

Divide the rice mixture into equal portions.

Shape each portion into a ball or triangle.

Wrap each rice ball with a strip of toasted nori seaweed.