A series of images based on the flower language of roses:

• A single rose: It indicates “Love at First Sight”
• 2 Roses: Give 2 roses to show that you are deeply in love with them
• 3 Roses: I Love You
• 4 Roses: To Signify nothing will stand between the two of us.

Source: https://www.flowersandkisses.com.sg/meaning-behind-the-number-of-roses

Based on Episode 12 of the anime, where Misumi Hatsune is gardening, and drops 4 roses when Togawa Sakiko finds her. Sakiko then proceeds to pick these up while talking to her.