Koi wa Deep ni

Composer

• 
  Kanno Yugo

Director

• 
  Suzuki Yuma
• 
  Iwamoto Hitoshi

Screenwriter

• 
  Tokuo Koji

Main Role

• 
  Ishihara Satomi

  Nagisa Mio

  Main Role
• 
  Ayano Go

  Hasuda Rintaro

  Main Role

Support Role

• 
  Hashimoto Jun

  Kamoi Tadashi [Mio's uncle / Laboratory manager]

  Support Role
• 
  Otani Ryohei

  Hasuda Kotaro [Rintaro's older brother / Managing director of "Hasuda Trust"]

  Support Role
• 
  Watanabe Keisuke

  Hasuda Eitaro [Rintaro's younger brother / "Hasuda Trust" Resort Development Headquarters employee]

  Support Role
• 
  Imada Mio

  Miyamae Aika [Mio's friend / Project researcher]

  Support Role
• 
  Takahashi Tsutomu

  Someya Daigo [Professor specialising in fish ecology]

  Support Role
• 
  Mizusawa Shingo

  Shiiki Takuma [Associate professor specialising in marine renewable energy]

  Support Role
• 
  Kaga Takeshi

  Hasuda Taro [Father of the Hasuda brothers / Chairman & President of "Hasuda Trust"]

  Support Role
• 
  Fujimori Shingo

  Tsurukawa Yusaku [Rintaro's best friend / Public relations department]

  Support Role
• 
  Kakei Miwako

  Yamauchi Karen [Resort Development Headquarters Planning Support Division member]

  Support Role
• 
  Matsukuma Tsurumatsu

  Kazama Midori [Resort Development Headquarters Planning Support Division chief]

  Support Role
• 
  Fukuyama Shodai

  Mr. Enishi [YouTuber]

  Support Role
• 
  Kirishima Reika

  Hasuda Arisa [Rintaro's mother]

  Support Role
• 
  Uenoyama Yumeki

  Hasuda Rintaro [Young]

  Support Role
• 
  Nagano Sora

  Hasuda Kotaro [Young]

  Support Role
• 
  Iwakawa Haru

  Hasuda Eitaro [Young]

  Support Role
• 
  Wakamoto Norio

  [Spotted moray eel] [Voice]

  Support Role
• 
  Izumi Rika

  Omiya Haruka [Rintaro's sister-in-law]

  Support Role
• 
  Nishimura Miyu

  Yabe Nana

  Support Role
• 
  Hosoya Yuta

  Sakai Daisuke

  Support Role

Guest Role

• 
  Sakura Ichika

  [Tadashi's partner] (Ep. 1)

  Guest Role
• 
  Yoshida Oolongta

  ["Twilight TV" MC] (Ep. 1, 3, 7)

  Guest Role
• 
  Kote Shinya

  David Chan [Chairman of "Benjamin Star Hotel"] (Ep. 2)

  Guest Role
• 
  Hotta Mayu

  Makabe Yukino

  Guest Role
• 
  Kaji Yuki

  [Fourspine Sculpin] [Voice] (Ep. 3)

  Guest Role
• 
  Miyazaki Tomu

  Makabe Akio [Yukino's uncle] (Ep. 3)

  Guest Role
• 
  Hanazawa Kana

  [Moon Jellyfish] [Voice] (Ep. 5)

  Guest Role
• 
  Terada Azuki

  Yuri [Little girl at aquarium] (Ep. 5)

  Guest Role
• 
  Koshimura Tomokazu

  [Reporter] (Ep. 5)

  Guest Role
• 
  Fujiyoshi Kumiko

  Tomiura Fumi [Director of "Tomiura Clinic"] (Ep. 6, 8)

  Guest Role
• 
  Yamada Meikyo

  Sanada [Professor at Shibaura Marine University] (Ep. 6-8)

  Guest Role
• 
  Nagakura Daisuke

  Katagiri [Scientist] (Ep. 6-8)

  Guest Role
• 
  Ogata Megumi

  ["Kameda"] [Voice] (Ep. 6)

  Guest Role
• 
  Oomizu Yousuke

  [Courier] (Ep. 6)

  Guest Role
• 
  Horibe Keisuke

  Takayanagi [Director of weekly magazine "High Tide"] (Ep. 7)

  Guest Role
• 
  BOB

  Hishida [Takayanagi's subordinate] (Ep. 7)

  Guest Role
• 
  Sumida Takashi

  Kondo [Attendees at the faculty meeting of Shibaura Marine University] (Ep. 8)

  Guest Role
• 
  Tanaka Hanna

  [Little girl] (Ep. 9)

  Guest Role
• 
  Shiina Ryo

  (Ep. 9)

  Guest Role
• 
  Nishina Mirei

  (Ep. 9)

  Guest Role
• 
  Komagine Kiita

  Visitor

  Guest Role
• 
  Kawai Yasushi

  Hiramatsu Yuki (Ep.1)

  Guest Role
• 
  Nakagawa Akira

  [ER team member] (Ep. 4)

  Guest Role
• 
  Yuki Hina

  (Ep. 5)

  Guest Role

Unknown

• 
  Furuya Kazuki Unknown
• 
  Kunimatsu Airi Unknown
• 
  Shimizu Kotoko Unknown
• 
  Morozumi Renon Unknown
• 
  Eguchi Sota Unknown
• 
  Oguma Taiki Unknown