He likes colored grass so bring him at least one every day, and show him your dog or cat. After a while when you go his house he will introduce you to her.
Maybe if you make friends with Daryl, then go in his basement, you can meet the mermaid.
Befriend Daryl 250+ and then go to the basement of his house. It will be unlocked and you'll get a cutscene.
About 250.
There is no mermaid in Harvest Moon A Wonderful Life. In Harvest Moon DS which is set in the same town, there is a mermaid named Leia.
Leai is a she mermaid. if you get darhyl at 100 fp youll be able to meet her in his basement.
You have to befriend the scientist Daryl he likes colored grass and he lives by the sculptor David. They live below the town above the beach. Hope I helped. -WPrincess Luv
He is the scientist who lives just south of the main town area.
>>
12 days
WARNING, SPOILER: He keeps the mermaid Leia in his basement. Befriend him to unlock it.
exactly 2pm
Get Daryl (the freaky scientist who lives in the tin house) to 100 FP. He likes grass a lot and also your dog. Once you get to 100 FP (you will know because he will start telling you different things) press A in front of the trapdoor in the left corner. It sort of looks like a vent... This will lead to the basement, and the mermaid, Leia, will be in a bathtub there. If Daryl gets below 100 FP, I think it locks again. Just talk to him whenever you see the mermaid and it should be fine.