- Name: Big the Budō (ビッグ・ザ・武道)
- Real Name: Neptune King (ネプチューンキング)
- Nickname: Perfect Master (完傑 Kanketsu), Perfect Chōjin Don
- Classification: Perfect Chojin
- Homeland: Japan
- Age: over 100,000
- Height: 290 cm
- Weight: 320 kg
- Chojin Kyodo: 50,000,000 Power
- Trademark Techniques: Megaton King Drop, Budō Exploding Kick
- Tag Teams: Hell Missionnaires (Neptuneman)
- First Appearance: Manga Chapter 209 (disguise) and 218 (Big the Budō)
- Submitted by: Kazuya Mitani (三谷和弥) of Aichi.
- "Graydar" disguise submitted by: Koji Nishikawa (西川興治) of Miyagi.
- "Mildman" disguise submitted by: Mitsunori Tamashiro (玉城光則) of Osaka.
- Megaton King Drop (メガトン・キング落とし, Megaton Kingu Otoshi)
- Budo performs a double underhook and jumps into the air with his opponent then shifts his weight so he is standing on the soles of their feet and drives them into the floor wih the added force of his magnet power.
- Budō Exploding Kick (武道爆裂キック, Budō Bakuretsu Kikku)
- Magnetic Storm Driver (磁気嵐ドライバー, Jiki Arashi Doraibaa)
- Budo leaps into the air, uses his magnet power to draw the opponent up and performs a power bomb on them.
- Quarrel Bomber (喧嘩ボンバー)
- Like Neptuneman he executes a magnetically charged lariat on his opponent.
Neptune King was originally a student under the one of the original Perfect Chojin, Psychoman, who taught him how to use Magnet Power. Becoming a member of the Perfect Large Numbers, he eventually grew arrogant and was stripped of his rank by Psychoman. After this, Neptune King left with his group of subordinates, which he labelled as the main Perfect Chojin.
Having left the Perfect Large Numbers, Neptune King entered Chojin Tournaments within the mortal realm. However, he became disgusted as the competition shifted from strong vs. weak death matches into a commercialized sport. He then went into hibernation under in the River Thames. He remained there for millions of years until he was discovered by a Chōjin named Quarrelman. Quarrelman was trying to commit suicide by jumping into the river because he couldn't find any opponents strong enough to defeat him (even Robin Mask was too easy for him). Together, the two of them plotted to bring the Chōjin competitions back to its bloody roots. The Neptune King gave Quarrelman his Neptune Mask, making him Neptuneman, and created a new Bōgu-clad identity for himself- Big the Budō.
Dream Chōjin Tag Arc
He and Neptuneman entered the Universal Tag Team Tournament as the Hell Missionaries with the intention of stealing the masks of the Chojin champions and give them to their henchmen, so that 'Kinnikuman' and 'Robin Mask' would be their henchmen, if only in name. They appeared disguised at the beginning, revealing themselves to punish Screw Kid and Kendaman for their loss against the 20 Million Powers, Buffaloman and Mongolman. They faced the Chojin Master-Student team of Robin Mask and Warsman, who they beat and stole their masks. In the next round they fought the 20 Million Powers, ultimately defeating them and unmasking Mongolman to reveal Ramenman. In the final round, they fought the Muscle Brothers, Kinnikuman and Kinnikuman Great(Terryman in disguise), in a three round match. In the first round, He and Neptuneman won by Cross Bomber, revealing Kinnikuman Great to be Terryman, who had taken the role after the real Great, Prince Kamehame, died. however, they lost to Kin and Terry in the next rounds, when Big began using the swords in the 'Sword Floor Death Match' he designed. This caused Neptuneman to turn on him, as using weapons was against the rules of Perfect Chojin.
Scramble for the Throne Arc
When the Five Evil Gods discussed Kinnikuman's growth in power, one of them revealed the corpse of Neptune King as testament to it, with several of the Gods remarking how unbelievable it was for the 50,000,000 power Perfect Chojin to be defeated by Kinnikuman.
A character appearing to be Big the Budo is seen in flashbacks concerning the DMP's training, suggesting that he was one of the founders, as head of the Perfect Chojin division, similar to how Sunshine was head of the Akuma Chojin division. This may have been Strong the Budo.
- Big The Budō had a total of three disguises and four masks, (Hell Missionary, Mildman, Big the Budo, Neptune King mask) the mask of his last disguise got shattered by a double Kinniku Buster and revealed he looked like an older version of Neptuneman with a golden mask. This later got shattered by the winning Muscle Docking from Terryman and Kinnikuman, revealing an old face that looked almost as if he were dead for long time.
- Favorite Food: Sushi
- Theme Song: "Mask Hunter" (覆面の狩人, Fukumen no Karyūdo) by Takayuki Miyauchi (feat. Yonehiko Kitagawa as Big the Budō)
- Win/Loss Record (Singles)