The story begins with the arrival of a brave young boy in Paris. His ambition is to join the glorious Imperial Guards, but fierce competition and the minimum age requirement hinder him from joining. The boy then challenges the well-known Three Musketeers in order to demonstrate his excellent skills with the sword. However, at the very moment the fight begins, a power-hungry group cuts in. Realizing their wicked intention, the boy D'artagnan and the Three Musketeers quickly cooperate and defeat them. This is the beginning of their friendship and commitment to fight conspiracy.

The Inuyama Family, along with their pet dog Tetsunoshin moves to the famous Hoppongi Hills (modeled after Roppongi Hills) from Kyushu. Rumi Inuyama's father owns an IT Company in Japan and is a step further to becoming number one. However, Tetsunoshin learned that his master's family loaned a lot of money renting their home in Hoppongi Hills, almost to the point of the whole company becoming Bankrupt. To make things even worse, the whole family spends a lot of money on everything, making Tetsunoshin's problems worse. To solve this problem, Tetsunoshin teamed up with the Hills Dogs and will do anything to pay all the Inuyama Family's expenses. (Source: Wikipedia)