Lewis and Marnie have a very close relationship. Although Marnie claims to be single during the Flower Dance, another questline raises some suspicions between the two. Lewis visits Marnie to attend to her "business needs" on occasion, and they can often be found drinking together at the Stardrop Saloon in the evening. You can even find Lewis' shorts in her room, and that's spicy enough to confirm something.
Marnie greets the player as they come out of the farmhouse. She will tell the player that she is trying to train her goats to say "hello" but they will not cooperate unless she has their favorite food, Cave Carrots. Marnie asks the player to bring one to her ranch between 9 AM and 5 PM. If the player enters Marnie's Ranch during that time (opening hours may contradict this) with a Cave Carrot in their inventory, a cutscene will occur with the player giving Marnie the carrot. This cutscene will trigger regardless of whether or not Marnie is home.
Three Hearts II
After reaching 3 hearts, Marnie sends you a recipe in the mail. She also begins sending you hay in the mail.
After entering into Pelican Town after 7PM, you will appear behind Lewis' house. Lewis and Marnie are talking by the river about making their romance public. Lewis says it would undermine his authority, while Marnie says he's too concerned for his job. In the end, Marnie says she'll keep their relationship a secret. Afterwards, you'll pop up and scare both Lewis and Marnie. Lewis asks you if you heard anything, and you are presented with a choice. If you choose to keep the secret, Lewis will thank you. If you say you'll tell everyone in town, Lewis will cry. Afterwards, Marnie will ask why you were behind the house, and your character will run away, leaving the two alone and confused.
No change in relationship occurs if you say you will keep the secret with Marnie or Lewis.
Seven Hearts
After reaching 7 hearts, Marnie sends you a recipe in the mail.