Diamond no Ace Wiki
Miyauchi Keisuke
Seidou High School - No. 12
Bats: Right Throws: Right
Kanji 宮内 啓介
Nickname Miya-chan (by Ryousuke)

Miya-san (by Miyuki
Muscle-senpai (マッスル先輩) (by Sawamura)
Muscle-paisen (マッスルぱいせん) (by Sawamura)

Gender Male
Age 17 (debut)

18 [1]

Date of birth 31 August
Place of birth Saitama Prefecture
Bloodtype O
Height 176 cm (5' 9")
Weight 80 kg (176 lbs)
Education Third Year High School (debut)

Seidou Alumnus [2]

Class 3-C
First Appearance
Manga Act I - Chapter 30
Anime S1 - Episode 12
Voice Actor Taishi Murata
I'm not interested in a second-string game.
Miyauchi to Ryousuke

Miyauchi Keisuke comes from the Saitama prefecture and was a third year student of Seidou High. He was the reserve catcher of the First-String of the Seidou High School baseball team.


Miyauchi has short black hair with a short tail end behind. He is the only character in the series who snorts out from his nose (Sawamura followed him to do so later) which means he's either saying something serious, or he's irritated, pumped up or just doing anything that makes him exert effort.

He has a huge build which is attributed to his daily rigorous practice even after training. Miyauchi may look scary but is not as scary as Isashiki.


Miyauchi does not talk much. But when he does, he says the most important things in the shortest way.

He was a member of the "Hopeless Generation" 1st-Year students that entered Seido's team, and by comradery and sheer self-determination they improved themselves to become a team with the potential to make nationals. Miyauchi was thin boy and was advised by his upperclassman to take up bodybuilding so that he could withstand the home plate collisions he would be subject to as a catcher. He took that advice to heart and dedicated himself to bodybuilding and baseball training with his year mates. Although he received playtime on the field during practice games, his primary job during tournament games was as the reserve catcher who made sure relief pitchers were ready to play when needed. Deep inside, he knows Miyuki and Chris are catchers he may not be able to catch up to. However, he's the type of player who strives harder when surrounded by talented guys. Miyauchi, as commended by Chris, is a member with a very strong fighting spirit.

Despite being inferior to Miyuki in terms of baseball skills, he is a dignified player whom the former respects and feels threatened on several occasions after they retired. He acknowledges that in comparison, his abilities as a batter, and to call plays is not equal to his younger teammate's. But Miyauchi is very practical and is determined not to allow that fact to distract him to the point of affecting his performance as a catcher. He also reminded Miyuki of his role as captain who has to look after his pitchers, specifically calling his attention to help Kawakami.

After the summer tournament, Miyauchi still occasionally visits the team and always reminds Miyuki of his tasks as the new captain. He is the 3rd years' official catcher during the 3rd years vs. current members intrasquad game


His sense as a catcher is inferior to Miyuki's, but his catching skills are high. Miyauchi is good at meeting the opponent's runners with a rebuff thanks to his thoroughly tempered body. He trains persistently and in silence.

Towards pitchers, he tries his best to use their potential and known skills. He is especially supportive of Tanba, who had asked his help to develop his forkball. Towards Kawakami, he's a bit peculiar. Miyauchi once grabbed Kawakami's balls to help him regain his confidence.

Miyauchi has little difficulty catching Sawamura's pitches and is also able to catch Furuya's fastballs since he had been catching 150 km/h balls from pitching machines.

Before Miyauchi retired, he was able to participate in some important practice and preliminary games, but little is shown when he's at-bat. 

Player Statistics[]

This data is based on the official guidebook, it will only be changed if there is an official update!

Player Statistics
Note that just because a character said something about another characters improvements is not considered an official update!
You are free to write about the characters improvements in the Skills section above!
Physical Strength
Mental Strength


  • Favorite Food: Sasami, Egg whites [3]
  • Favorite Subject : Science in general [3]
  • He likes unicorn beetles and his hobby is muscle training. [3]
  • He respects Sawamura Hirokazu [3]
  • He is disliked for often grabbing the pitchers nether region as a means to ease their tension. [3]
  • After graduating, he is last seen joining a Mixed Martial Arts gym. [4]



  • "I'm not interested in a second-string game." - to Ryousuke [7]
  • "You've made it this far and there is no relief in sight. But you'll be fine. You've lost some of your velocity but you've pitches all game. Have some confidence!" - to Kawakami [8]


  1. Act I - Chapter 220
  2. Act I - Chapter 412
  3. 3.0 3.1 3.2 3.3 3.4 Official Guide Book - Omote
  4. Act I - Epilogue 3 "Brand New Day"
  5. Act I - Chapter 54
  6. Act I - Chapter 364
  7. Act I - Chapter 30
  8. Act I - Chapter 53