Two brothers aged 8 and 6 recently conquered all 100 summits of Nihon Hyaku-meizan (100 famous mountains in Japan) with their grandfather, taking just two years and four months to do it.

Though no formal records are kept, a spokesman for the Japan Mountaineering Association said it has never heard of anyone as young as the two boys reaching all 100 mountain summits.

The 100 mountains were popularized by mountaineer and writer Kyuya Fukada in his 1964 book "Nihon Hyaku-meizan." Completing all 100 has since become the holy grail for climbers.

Yuto and Takuto, who hail from Fujimino, Saitama Prefecture, are the eldest and second son of Junichi and Kyoko Matsumoto.

The two boys and their grandfather Kaoru, 63, began their big challenge in July 2007, tackling Mt. Nikko Shiranesan on the Gunma and Tochigi prefectural border.

They climbed 28 mountains in 2007, and 43 mountains in 2008, including Mt. Yoteizan in Hokkaido, their 50th peak.

The boys spent 28 days trekking up mountains during their summer vacation in 2009, including the nation's highest, Mt. Fuji.

In October, the boys made their way to the summit of Mt. Kitadake in Yamanashi Prefecture, the nation's second-highest peak, where they finally were able to celebrate their century of climbs.

While the brothers said they were happy to have achieved their goal, they admitted they had really wanted to go to Disneyland.

Yuto began climbing at the age of 5 when his grandfather invited him on a hike. Younger brother Takuto then asked if he could come along, too.

Before starting their 100-peak challenge, the brothers spent six months training, and they developed a set pattern when walking together: Yuto leads the group when ascending and Takuto takes over when descending.

The two do not always cooperate though, admitting they occasionally fight, which sometimes ends in tears or someone refusing to budge. But in the end they always finish the trek under their own steam.

The boys have become well known among the climbing fraternity and are sometimes asked to pose for photographs.

Kaoru said he enjoys the climbing with his grandsons, saying it is what he lives for.

Yuto expressed a similar love for climbing. "I most love the moment when we eat lunch atop a mountain."

Takuto said he is most proud of having spotted such animals as a rock ptarmigan and a whistling hare while in the mountains.

The boys said they hope to do a climb next year with their youngest brother Naoto, who at the age of 2 is nearly ready to join in the fun.