Anime and Manga
In the story, the anime and manga has the same concept. He found Ginji and Ban and fed them. Despite of his sickness, he manages to live with his own. After Ginji and Ban introduced themselves in the old man. In the manga, the old begged to bring his daughter back and the Get Backers accepted it right away. In the anime, he begged also but Ban refused. However, Ginji can't take it so he decided to help the old man. While Ban came along since he can't leave Ginji by his own since they are the Get Backers.
The Get Backers managed to go in the mansion where Rika is. They found Rika but was betrayed by her. And Rika stated that she doesn't need the old man who is his father. Ban and Ginji was killed but later on, Rika woke up and it was just a bad dream by Ban's evil eyes.
They tried to force Rika to come with them to see her father, but she didn't come with them. When the Get Backers came back they found the place of the old man with ambulances. In the manga, a group of people went to his place and tortured him, while in the anime, his sickness attacked him.
At the end of both anime and manga, Ban used the evil eyes on him. As the old man thought he saw his daughter but it was just an illusion. In the manga, it was showed that the old man died.