Umi's face when she resigns herself to the fact that Honoka and Kotori fell for Nico's scheme is the best.
To be fair, Kotori knows it's Nico's scheme and Honoka probably does, but they don't care.
By the way I always thought, in canon, Nico was more honest and loving - always glomping Maki - and Maki was aloof, dishonest, and stereotypically tsundere. But in this one, Nico's being utterly dishonest, and Maki's being all kind and honest and sweet. Which surprises me. Like it would kill Nico to say Maki's cute and she's grateful to her. Apparently it would.