Chelsea is a playable character from Dragalia Lost.
A sylvan girl obsessed with Luca (or "Luccy"). She sticks to him like a shadow, and doesn't seem to know when to stop. That can all be quite tiresome, but she must have a good reason, right?
Official Description (Valentine's Chelsea)
All wrapped up in a sweet chocolate dress, Chelsea once again treads the rocky road of love. Valentine's Day is her do-or-die chance to shower "Luccy" with affection. It's anyone's guess what terrifying—er, touching gift she'll give him next.