Hell's Tormentor Kraken

The young man troubled by his difficulties in finding employment, Shimizu Kuuma, suddenly finds himself in another world. Being taken into the women-only prison, the Sea Bastille, Kuuma gains a huge power after fusing with the ruler of the sea, the monster called Kraken. Having been entrusted by the Kraken to save Princes Zeina, Kuuma infiltrates the the Sea Bastille. However, what awaited him there was female prisoners full of quirks...