After the party entered the underwater cave, everything becomes dark because the sunlight doesn't reach inside the cave.
When they just started to worry about what they should do, a little ball of light appeared near them, lightning their way through the cave.
Hello Kitty, luckily, know the skill [Cast Light], and she used this skill to cast the ball of light to illuminate an area 30 meters radius around them. The ball of light will follow the caster whenever she goes.
Many utility skills don't have attack power but are indispensable in various situations in the game, like [Cast Light], [Warmth], [Flash], and others.
Now that they have a way to see in the dark, they can continue their way through the dungeon.