Akafucrystal

Spoiler Warning: Spoilers for RobiHachi may follow.

Akafucrystals. Mass-produced fake (top) and authentic, found in the wild (bottom).

An Akafucrystal is sacred crystal of Isekandar, said to bring good fortune to those who own it. Akafucrystals can be obtained through donating offerings to the Isekandar Shrine. However, it is revealed those given to visitors are fake, mass-produced from polymer resin.
Real, small Akafucrystals can be still found on Isekandar. Robby accidentally trips over one without realizing it, as it was enclosed in regular stone. There is also a small shrine to a slightly bigger Akafucrystal, which was where the local people of Isekandar used to pilgrimage to before Dontsu turned their planet into a tourist spot and decided it was not impressive enough.
Fake Akafucrystals are red, while real ones are predominantly red but sparkle through various colors.