在外太空的邪惡外星人，將娜裘行星(NAJU)往地球推進。此舉引起許多人的恐慌，為了避免人類的滅亡，機械女戰士嘉蒂(D.P. System)奉命前往娜裘星，破壞內部的十個安全設備 ，讓行星自行引爆。每個裝置隱藏在21個狹窄通道上，還有可怕的怪獸進行看管，需要將怪獸們打倒後才拿到鑰匙，往下個關卡前進。嘉蒂是否能成功完成任務，順利平安歸來? 當通過第一個射擊舞台後，登入娜裘行星後，就會收到一個遺言訊息，表示星球上的所有人都被邪惡的外星生物殺死，留言者準備要去啟動引爆裝置，如果不幸失敗，希望嘉蒂可以完成引爆任務，於是遊戲正式拉開序幕.......

嘉蒂初代(The Garlic)於1986年的MSX主機推出，畫面採用小關卡移動方式進行， 主要任務是消滅敵人，有時候還需要取得所有補給，才能切換到下個關卡，整體銷售量及評價普通。之後發行的嘉蒂外傳，在任天堂紅白機推出後，則融入許多創意的設計，主角是人機一體的機器人，關卡會從射擊舞台切換到作戰畫面。整體遊戲設計太過複雜，因此有接關密碼選項的設定。如果只想單純玩射擊關卡，可以輸入日版遊戲的"えいえるじい"(ALG:Another Legend of Guardic的縮寫)或是美版遊戲的"TGL"(縮寫是The Guardian Legend)，就可省去機器人的舞台，須注意當全破時，右下角的畫面就不會出現女主角照片。 

按B鈕就可進行射擊，轉成作戰畫面時，按Select就可選擇武器跟確認方位，A紐發射特殊武器，B紐則是標準雷射。射擊舞台總共有22個，拿到紅色小精靈能增加八格能量槽。能量最高可以增加到32格，受到攻擊或是碰到敵方，都會造成損傷。沿路都有補給，總共有九種，有時候是需要消滅敵人後才會出現。拿到紅心可以提升四格能量，取得最強的能量補給，則可瞬間補充所有能量。取得連發器，子彈就能連發射出。若轉換成機器人的狀態，可以使用的特殊武器有12種，都有數量上的限制，能量歸零的時候就會爆炸，若看到可擊碎的磚塊可以射擊看看，或許會有意想不到的驚喜。 

如果是輸入密碼的話，射擊關卡的順序會是:第0關的Boss由11個藍色武器圓筒跟四個方塊射擊炮組成，射擊的時候會打開開關，這時候拼命射擊就會造成敵人的重傷害。第1關水中世界開始，整體難度大幅增加。之後分別跳到的第11關、第12關，植物世界第2關、第13關、第3關、第14關、第4關，冰結世界第15關、第5關、第16關、第6關，生物世界第17關、第7關、 第18關、第8關，石化世界第19關、第9關、第20關、第10關、第21關、第22關。

到後期的時候會發現，有一些Boss被擊敗後，下個關卡又出現。最後第21關會出現許多過去擊敗過的Boss，相當難纏。第22關的Boss弱點在手臂，需要避開子彈跟手的攻擊，造成重傷害後就會變成全身橘色，然後是紅色，持續射擊就準備迎向全破畫面。在機器人舞台，所要通過的關卡有1.水中世界A+B 2.植物世界A+B 3.冰結世界A+B 4.生物世界A+B 5.石化世界A+B。  

嘉蒂外傳的遊戲開發商Compile之後倒閉，將相關業務移轉到Compile Heart，母公司為Idea Factory，嘉蒂外傳是Compile與irem一同合作的神作，irem後來放棄遊戲開發，專注在博弈機台的生產製造。D4 Enterprise於2010年10月28日取得Compile大部分的遊戲所有權，不包含魔法氣泡跟Aleste，嘉蒂外傳困難度相當高，許多關卡還有特定任務的設定，直到今天許多玩家們仍給予極高評價。同年1988年在任天堂推出的另一款經典遊戲~超惑星戰記（日" 超惑星戦記 メタファイト/ Blaster Master)， 也是採用人機分離的模式設計，這兩款遊戲直到現在仍受到許多玩家喜愛。如果當年的月風魔傳，都在2021年的STEAM發行續作，那麼有一天看到嘉蒂外傳的續作推出，玩家們大概也不用感到太意外。

In outer space, a group of evil aliens begins pushing the planet NAJU toward Earth, triggering widespread panic among humanity. To prevent total extinction, a mechanical female warrior named Guardy (the D.P. System) is dispatched on a critical mission: infiltrate NAJU and destroy ten internal control devices, causing the planet to self-destruct. Each of these devices is hidden within a network of 21 narrow corridors, heavily guarded by terrifying monsters. Only by defeating these creatures can Guardy obtain the keys needed to advance deeper into the planet. Whether she can successfully complete her mission and return safely remains uncertain.

After clearing the first shooting stage and landing on NAJU, the player receives a final message left behind by a fallen individual. It reveals that all inhabitants of the planet have already been slaughtered by the alien invaders. The sender intended to activate the self-destruct system themselves, but fearing failure, entrusts the mission to Guardy. From this moment, the story fully unfolds.

The original The Guardic was released in 1986 on the MSX platform. Its gameplay was based on small segmented stages, with the primary objective of defeating enemies and sometimes collecting all supplies to progress. Overall, its sales and reception were average. Its successor, The Guardian Legend, released on the Nintendo Famicom, introduced many innovative elements. The protagonist became a humanoid combat android, and the gameplay alternated between shooting stages and exploration/action sequences. However, due to its complexity, the game included a password system to allow players to continue progress.

For those who prefer to focus solely on shooting stages, entering specific passwords enables this mode. In the Japanese version, entering “えいえるじい” (ALG, short for Another Legend of Guardic), or in the English version, “TGL” (The Guardian Legend), skips the exploration sections. However, doing so means that upon completing the game, the heroine’s portrait will not appear in the ending screen.

In terms of controls, pressing the B button fires the standard weapon. During exploration mode, pressing Select allows players to choose weapons and check positioning. The A button fires special weapons, while B remains the standard laser. There are a total of 22 shooting stages. Collecting red power chips increases the energy gauge by eight units, with a maximum capacity of 32. Taking damage or colliding with enemies reduces energy. Along the way, players can find nine types of power-ups, some of which only appear after defeating enemies. Heart items restore four units of energy, while the strongest energy item fully replenishes the gauge instantly. Rapid-fire upgrades allow continuous shooting.

When switching to the humanoid combat form, players gain access to 12 types of special weapons, each with limited ammunition. If energy reaches zero, the character explodes. Players can also destroy certain blocks, which may reveal hidden surprises.

When using the password system, the order of shooting stages changes significantly. Stage 0 begins with a boss composed of 11 blue weapon pods and four turret blocks; shooting opens its core, allowing players to deal heavy damage. From Stage 1, the underwater world, difficulty increases sharply. The progression then jumps across various stages in a non-linear sequence, including plant, ice, biological, and petrified worlds.

In the later stages, some bosses reappear even after being defeated, increasing the challenge. Stage 21 features multiple previously defeated bosses, making it particularly difficult. The final boss in Stage 22 has a weak point in its arms; players must dodge attacks while dealing damage. As the boss changes color from orange to red, continuous attacks will eventually lead to victory and the ending sequence.

In the exploration (robot) stages, players must clear five themed worlds: underwater, plant, ice, biological, and petrified—each divided into two areas (A and B).

The game was developed by Compile, which later went bankrupt. Its business operations were transferred to Compile Heart, a subsidiary of Idea Factory. The Guardian Legend was a collaboration between Compile and Irem, the latter of which eventually withdrew from game development to focus on pachinko and slot machine manufacturing. In 2010, D4 Enterprise acquired most of Compile’s intellectual properties, excluding titles like Puyo Puyo and Aleste.

Known for its high difficulty and unique mission-based structure, The Guardian Legend continues to receive strong praise from players even today. Interestingly, another classic Famicom game released in 1988, Blaster Master, also featured a similar mechanic of switching between vehicle and on-foot gameplay. Both titles remain beloved among retro gaming fans. Considering that GetsuFumaDen received a modern sequel on Steam in 2021, it wouldn’t be too surprising if The Guardian Legend were to receive a revival someday as well.