Overview

The Marunouchi Line (M), opened in 1954, was Tokyo's second subway line, linking Ogikubo and Ikebukuro over about 24.2 km and 25 stations. Its red trains cut through Shinjuku, Tokyo Station, and Ochanomizu — briefly surfacing near Ochanomizu to cross the Kanda River valley, one of the line's few above-ground stretches.

On a map the line looks like someone drew a U and then lost their nerve: from Ikebukuro it dives south to Tokyo Station, swings west through Kasumigaseki and Shinjuku, and heads out to Ogikubo. That detour is not an accident of terrain. The route was drawn to serve the government district and the Marunouchi business quarter on the way, which is why a line connecting two points on the Yamanote's western half insists on visiting the middle first.

Along the route

The line strings together the residential streets of Ogikubo, the bustle of Shinjuku, the government offices of Kasumigaseki, the Marunouchi side of Tokyo Station, and the sub-center of Ikebukuro — covering nearly every major hub on the west side of central Tokyo.

The Ochanomizu crossing is the moment everyone remembers. The train leaves the tunnel, runs in daylight across a bridge over the Kanda River with the Chuo Line directly overhead and the Sobu Line below, and dives underground again seconds later. Three railways at three heights in one glance — it is the most photographed twenty seconds of subway in Japan, and it happens because the valley walls were too steep to tunnel through in 1954.

Where the typing gets hard

Twenty-five stations, 283 keystrokes, an average of 11.3 per stop. That is the heaviest average of any line in this guide's shortlist, and the reason is visible at a glance: ten of its 25 stations contain a small ゃ/ゅ/ょ, far more than any comparable line.

The centre of gravity is the Shinjuku cluster. Nishi-shinjuku, Shinjuku, Shinjuku-sanchome (shinjukusanchoume, 17 keystrokes — the longest on the line) and Shinjuku-gyoemmae (shinjukugyoenmae, 16) arrive one after another. Four stations, four variations on the same stem, and the only thing distinguishing them is the tail. Losing track of which Shinjuku you are on is the classic Marunouchi mistake.

Kokkai-gijidomae (kokkaigijidoumae, 16) is the other big one, and the line's only sokuon: the small っ doubles the k in kokkai. Yotsuya-sanchome (yotsuyasanchoume, 16) sits right next to Yotsuya (yotsuya, 7) — two stations, adjacent, one nine keystrokes longer than the other.

Relief comes late: Ginza (5), Tokyo and Ogikubo are all short, and the eastern arc from Ginza to Awajicho moves quickly.

How to practise it

Start from Ogikubo heading toward Ikebukuro. That order gives you the four Shinjuku stations early, while your concentration is fresh — and they are what this line is really testing.

If you want to work specifically on long-vowel endings, this is the best line in the game for it. Ten stations ending in ちょう/きょう/じょう in a single run is more concentrated practice than any drill, and the game accepts both spellings throughout (sanchoume or santyoume).

Whichever start station you pick, a Marunouchi run always covers all 25 stations end to end, so times are comparable across every attempt.

Why play it

That above-ground crossing near Ochanomizu is the line's most memorable moment, and the mix of short and long station names is good practice for shifting typing rhythm on the fly.