Choukou Sennin Haruka: Haruka VS Escalayer by Alice Soft - Adult Sex Game

The story continues from the harem ending in Choukou Sennin Haruka, where protagonist Takamura ends up with all 3 heroines as his wife.

When the four of them are enjoying a nice trip to the beach they get information on a phantom’s appearance and head back towards the city. But on their way a mysterious fighter appears in their way. The one that appears in front of them is none other than Escalayer, the heroine of justice that has saved earth before!