Review: (Story-N/A) Plot - 4 - I am unsure whether or not this is just a non-canon OVA, a canon side story, or a direct continuation of the series. I'm going with the second option. No story here, just a plot about Masato getting amnesia... and then developing feelings towards his mother...? And Mamako sees nothing wrong with this and doesn't even tell him she's his mother... and instead feels happy when he tells her he loves her...? If the main series didn't already prove my notion that Mamako actually wants to be in an Oedipus incestuous relationship with her own son, then this is thefinal nail in the coffin. Other than that, this is just the fanservice episode, so don't expect much.
Characters - N/A (3) Same characters, just at the beach. We learned something rather concerning about Mamako though...
Visuals - 5 Same art style and quality of animation. It spikes slightly at the end however. The fanservice wasn't all that great in my opinion, but was still satisfactory.
Audio - 4.5 Pretty much the same.

Overall: This was alright. For a fanservice episode, it's pretty decent, and it didn't focus on the fanservice as much as I thought it would. It gets the narrative scoring off easy because this is a special episode.
O score: 4.1/10 | S score: 7/10 | Final score: 5.55/10 rounded to 6/10 for MAL score.