Last Friends deals with issues such as domestic violence, sexless couples, and other problems that people suffer today. The youths in this drama are all suffering from different issues. They come to live together in a share house.
Hair stylist assistant Michiru Aida comes across Ruka Kishimoto, her best friend in high school. Ruka is living in a share house with her friend Eri, and is aiming to become a motocross racer. Ruka invites Michiru to live with her in the share house, but Michiru declines because she has plans to start living with her boyfriend Sosuke Oikawa, who works at the child welfare division at the ward office.
The same day at the same store, hair & make-up artist Takeru Mizushima bumps into Ruka and picks up a cup that she dropped and broke. Takeru chases after Ruka to return the cup, but she mistakenly thinks that he's trying to pick her up. Ruka yells at Takeru and walks away.
Soon after this, Michiru moves in with Sosuke. She is filled with happiness when Sosuke promises he'll never leave her side, whatever happens. But one morning, Michiru wakes up to find Sosuke looking at her cell phone checking her text messages...