Heart is You are Umasou's main character.
He is a blue Tyrannosaurus with red thin streak over his body. His eyes are a purple color.
Heart is something of a confused character that, despite being raised by a Maiasaura family, begins devolping a taste for meat after eating part of Gonza's tail and even started to fall into predatory instincts.
When he first met Umasou, he first thought of fattening him up to eat him but changes his mind when starting to feel attached to the juvenlie ankylosaur after changing his mind by abandoning him and accepts him as his son. After saying that Umasou is delicious, the ankylosaur thought that was his name much to his confusion.
Heart is also very brave, as shown being able to take down Gonza and his group without breaking a sweat and fighting the much larger Baku.