Han Sen had always needed a hyper geno art for underwater fighting. To fight in the water was completely different to fighting on land. The effects of water pressure and resistances were considerable. The shift in the effectiveness of certain land hyper geno arts to how they performed in the water likewise very acute.
Han Sen had many S-Class licenses of the Saint Hall, so spending one more did not concern him much. And now here he was, arriving in the Saint Hall to purchase an additional hyper geno art.
Humans found it hard to hunt creatures in the water, so there were not many underwater-based hyper geno art to select from. Han Sen's choices were strictly limited.
Out of the eight underwater ones available, he picked one S-Class licensed hyper geno art. He did not dwell on the purchase too much, and quickly bought it outright.