Their shape and look can resemble some homemade soap bar slices. At room temperature, their sweetness and texture reminds me of microwaved red bean cake. :meow-melt:
They came in a variety of looks. They could be one solid color, opaque, slightly translucent, have red beans and/or black sesame inside, or be striped like the above pic. Mainly saw them in the colors white, green, brownish-red, brown, pink, and dark grey w/ black specks.
Closest thing I can think of is https://en.m.wikipedia.org/wiki/Y%C5%8Dkan
I've had agar jelly, and it wasn't the same texture. But if Yokan chews and stretches like soft mochi, there's a chance you're right.