Original title was 要石 (kaname-ishi). Keystone, foundation stone or capstone is a reasonable translation but this is a real concept and it has a wikipedia page under the original name so I figured I'd give it to you. Furinkan also has a video about it.

Furinkan notes that: "This is a double issue of Shonen Sunday, subsequently it took a week off from publication the following week." Also, I forgot to mention but MAO took a break after the first chapter of this volume, hence the dates being the way they are.

August 7th, 2019. Author's note:
"Q: What is a food that makes you say "I want to eat this during the summer!"?
A: Miyako soba."