ESP abilities are rare, however, [Absorption] is one of the rarest abilities there are. This ability allows its user to get abilities of other beings and things by consuming them. No matter how hard or poisonous something is, the person would be able to eat it.
The teeth could tear through the likes of iron and gold easily, while toxins would be restructured, rendered harmless and edible inside the body. The characteristics of whatever It's eaten, whether it be an item or another living being, would be absorbed and assimilated, so that the one that absorbed them could use the abilities as if they were their own.
The strength of the ability that was gained through absorption depends on the quality of the substance and its freshness.
On Day 80 Rou acquires the ability [Synthesis] that he uses to merge the different abilities acquired by [Absorption]. Which is quite convenient since [Absorption] starts to gather less and less abilities due to the gap of strength between Rou and most of his enemies.