rhea (summer) (fire emblem)
Rhea from Fire Emblem when dressed in her summer attire from the Fire Emblem Heroes 2020 Overseas Memories banner.
She wears a white bikini with decorative gold chains serving both as necklace and a sort of underbust from which hangs a black tassel, a white cape, and what seems to be a white sarong integrated to the top itself; white hair flowers forming a circlet, and white sandals.
Likely to include her "weapon" in the game, a set of percusors (one per hand) that vaguely resemble palm trees with purple foliage. Extremely likely to see her along with Summer Byleth, the main character of the Duo Unit she's part of - Summer Rhea isn't her own unit in-game.
Note that it's possible (especially for older artwork), to depict Rhea in a swimsuit without it being the one described above, in which case this tag should not be used.