Tamamo no Mae Swimsuit Lancer in her Second Ascension swimsuit from Fate/Grand Order. Her t-shirt is now wet and see-through, she wears a towel bearing her name over her shoulders, and her sun hat is a little more frayed at the edges compared to her First Ascension.
This particular Ascension is also available as a DLC costume for Tamamo in Fate/Extella Link, given the name Beach Flower in reference to her first battle skill in FGO.
Due to how similar Tamamo Lancer's Ascension swimsuits look, you want to see the aforementioned garments present in the image for this tag to qualify. If you're not certain, it is best to not use this tag.