由Taito於1986年8月8日發行在任天堂Famicom上的《六三四之劍》（Musashi no Ken / 六三四の剣 ただいま修行中），是改編自漫畫家Musashi no Ken的熱血劍道漫畫的動作遊戲。在紅白機早期非常罕見地結合橫向捲軸冒險與一對一格鬥對戰，不僅還原主角夏木六三四的成長歷程，也在對戰模式中呈現出極具策略性的劍道博弈。

設計巧妙地呼應原作的主題，分為兩個主要部分：前半段是「修行篇」，以橫向捲軸形式呈現，要在山林野外奔跑、擊碎障礙、躲避動物騷擾，並收集地圖上的劍道具以增強能力。這一階段的目的是在時限內抵達終點，為之後的全國大賽累積實力。後半段則是「對賽篇」，畫面切換成一對一的劍道競技場，要運用上、中、下段攻擊與防禦，抓準對手的揮劍空隙進行反擊，擊中頭、手或腹部就能得分。與一般格鬥遊戲慢慢削血不同，《六三四之劍》還原劍道一擊決勝負的緊張感，使每一場比賽都充滿氣勢。

故事劇情緊扣原作，講述出生於6月3日下午4點的夏木六三四，父母都是頂尖的劍道高手，被稱為「東北的鬼百合」與「岩手的虎」。六三四為了超越父親、成為日本第一劍士，踏上地獄般的修行之路，最終參加全國劍道大賽，對抗宿敵東堂修羅，目標是在大賽中奪冠，證明自己是當之無愧的劍道之王。

在視覺上採用可愛的SD二頭身設計，雖然像素點陣簡單，但角色動作非常靈活，漫畫中招牌的劍道護具和竹劍都被精準重現。音樂輕快有力，充滿1980年代運動畫那種積極向上的氛圍，讓玩家在修行與比賽之間都能感受到熱血與緊張的節奏。

在市場上獲得高度評價，評論家認為其對戰模式在當時極具前衛性，甚至可以單獨作為一款競技遊戲來研究，許多玩家聚在一起，不玩闖關，而是專心鑽研對戰中的心理戰。對於熟悉漫畫的玩家來說，能操作六三四練習連擊並在全國大賽中擊敗宿敵，是非常熱血的體驗。歷史上，它是紅白機早期最成功的運動漫改遊戲之一，其對戰模式的系統邏輯在某種程度上影響後來許多追求即時判定的動作遊戲。

最令人難忘的畫面莫過於在修行篇拼命奔跑躲避那隻討厭的小狗，最後在全國大賽決賽中與東堂修羅同時揮劍，在清脆的竹劍撞擊聲中決定勝負的瞬間。玩家至今仍會回想起為了練好「面」的精準打擊，對著牆壁練習無數次的那段熱血時光。

In 1986, Taito released Musashi no Ken: Tadaima Shugyouchuu (六三四の剣 ただいま修行中) on the Famicom, an action game adapted from the popular shonen kendo manga Musashi no Ken by Musashi no Ken. At an early stage of the Famicom era, it was exceptionally rare to see a game that combined side-scrolling adventure with one-on-one sword duels. The game faithfully recreated the growth journey of the protagonist, Natsuki Musashi, while also delivering strategic, intense kendo battles in the dueling segments.

The game is divided into two main sections. The first, known as the “Training Arc,” is presented as a side-scrolling adventure. Players guide Musashi through forests and wilderness, smashing obstacles and avoiding wild animals, all while collecting sword items to enhance his abilities. The goal of this stage is to reach the end within a time limit, building up strength and skills for the nationwide tournament. The second section, the “Tournament Arc,” shifts to one-on-one duels. Players must master attacks and defenses at high, middle, and low stances, carefully timing counters to hit the opponent’s head, hands, or torso for points. Unlike typical fighting games where battles slowly drain health, Musashi no Ken recreates the tension of real kendo, where a single strike can decide victory, making each match thrilling and intense.

The story closely follows the manga: Natsuki Musashi was born at 4:00 PM on June 3. Both of his parents are top kendo masters, known as the “Demon Lily of Tohoku” and the “Tiger of Iwate.” Determined to surpass his father and become Japan’s finest swordsman, Musashi embarks on a grueling training journey and eventually enters the national kendo tournament, facing his rival Toudou Shura with the goal of claiming the championship and proving himself as the rightful kendo master.

Visually, the game uses cute SD (super deformed) character designs. Despite the simple pixel graphics, the animations are fluid, and the manga’s signature kendo armor and bamboo swords are faithfully reproduced. The music is upbeat and energetic, capturing the vibrant spirit of 1980s sports anime, adding to the intensity and excitement during both training and tournament stages.

The game received high praise for its depth and innovative design. Critics highlighted the duel system as particularly advanced for its time, so much so that it could be studied independently as a competitive game. Fans often gathered not to play the side-scrolling stages, but to challenge each other in the duels, exploring the psychological strategy involved. For players familiar with the manga, executing combo strikes and defeating rivals in the national tournament provided a truly exhilarating experience. Historically, Musashi no Ken stands as one of the most successful early sports anime adaptations on the Famicom, with its duel system influencing many subsequent action games that emphasize real-time judgment.

The most memorable moments remain in the “Training Arc,” as players sprint to avoid a mischievous dog, and in the finals of the national tournament, where Musashi and Toudou Shura strike simultaneously. The crisp clash of bamboo swords deciding victory captures the essence of the game’s intensity. Fans still recall the countless hours spent practicing precise strikes against walls to perfect the “men” attack—a defining, passionate memory of their kendo adventure.