Matsumoto Jun (Hana Yori Dango, Tokyo Tower) plays Momo, the human pet. His character is fantastic, I love him. I admitted at first, I did doubt such actor like him could achieve playing the character Momo, but he aced it. I had already read Tramps Like Us so I am entitled to my opinions.

Oh yes, the character who played Hasumi Shigehito, the boyfriend - was fugly. His smile was the worse. It reminds me of the Joker in one of the Batman films. I kept on, "don't smile! stay puzzled\confused\unsure." (shudders)
The rest of cast are excellent. The plot was well-established considering the strange situation concerning the human pet. In the manga, Sumire has the balloons to think, ponder, and wonder all the time. We can read her thoughts. But in the tv series, a new character is added. He is the counselor of the company where Sumire works at. He also carry a longhaired chihuahua everywhere with him (think Paris but uglier.. no wait, prettier).

The philosophy on how one can give more love to a pet but not to a human being; just because of fear of showing oneself. Pets will love without any restriction whenas, humans will always have doubts and fears.