Itai no wa Iya nanode Bougyoryoku ni Kyokufuri Shitai to Omoimasu.

Synopsis

As Maple tries to catch up with Sally and Kasumi as they fight each other, they all end up falling into an underground dungeon, where they are bound together by a cursed chain that will kill all of them if just one of them dies. Working together to avoid some unbeatable snail monsters, the three clear the dungeon and free themselves from their chains, sharing the spoils of their victory between them. Later on in the event, Maple and Sally meet a player named Kanade, who gives them a hint that leads them to an underwater squid boss, which Maple defeats by poisoning the sea (and giving the game admins another headache calling her more of a final boss than the final boss). With Sally earning the remaining medals needed through PvP kills before the end of the event, Maple uses the skills she earned to enhance Syrup into a mobile fortress.

(Source: Wikipedia)