Hikara Walker by Splatoon 2 ハイカラウォーカー バイ スプラトゥーン2

"The book contains various artworks and design documents from both the Octo Expansion and the main game, including two storyboard-style manga, details about fashion designer Toni Kensa, an interview with (fictional) graffiti artists, an interview with the developers about Squid Beatz 2, and information about bands such as Chirpy Chips and Squid Squad."

"...this book is the book that was in the car of the deep sea metro of "Splatoon 2 Oct Expansion".