WMG / Argonavis

Mashu is Nayuta's father posing as his manager under a fake name to manipulate him.

When AAside comes out, either we'll get an event story where Nayuta learns that they're related and has to deal with the emotional consequences of being manipulated by the very father who abandoned him, or GYROAXIA's band story will tackle the subject.

• OP here, I’m starting to have doubts on this one. I don’t think Mashu is going to appear in the game and Iryuu Koga (a character from the manga, and the vocalist of the band Ren saw as a child) seems more likely to be Nayuta’s father. Also, Nayuta doesn't seem like the gullible type; even if his father were to disguise himself as a different person, he'd probably be able to recognize him.
• Jossed. Nayuta’s father is actually Iryuu Koga.

Sakutaro, Futa's beloved saxophone, is named after his deceased friend.

This could also explain why he dislikes hospitals.

• (Sort of) confirmed; Sakutaro is named after Futa’s late brother.

At some point Jun will get an Important Haircut as part of his Character Development.

Eye-obscuring bangs are typically associated with extreme shyness, and if Jun’s character arc focuses on him getting out of his shell (or maybe even an actual job), he’ll probably end up getting it cut to reflect his growth.

The band Ren saw at the music festival as a child was the band lead by Nayuta's father.

If this is true, there will be an event in AAside where this is revealed (rather than it being revealed in the main story).

• Confirmed; albeit partially. The band Ren saw, Syana, is led by Iryuu Koga, Nayuta’s father. However, this is only revealed in the manga adaptation, not the game.

Predictions for future covers

Argonavis

• "The Race Is On"
• "Reclimb"
• "Perfect Hero"
• "Make You Free"
• "Wow Wow VENUS"
• "Reset"
• "Sekai Wa Koi Ni Ochiteiru"
• "Gunjō Biyori"
• "Starry Heavens"
• "Break In To Break Out"
• "Wish" & "Love So Sweet"
• "Beloved Survival"
• "Makafushigi Adventure"
• "Cha La Head Cha La"
• "Dan Dan Kokoro Hikareteku"
• "Dragon Soul"
• "Genkai Toppa x Survivor"
• "Butter-fly"
• "Target ~akai shougeki~"
• "The Biggest Dreamer"
• "Fire!"
• "Departure" and "Hunting For Your Dream"
• "Egao No Mahou" and "Yumeiro Grafitti"
• "Hikari E" and "Brand New World"
• "Haruka Kanata", and "Sign"
• "Youthful" and "Hologram"
• "Change The World"
• "Kimi Ga Inai Natsu"
• "100% Yuuki"
• "Kawaita Sakebi" and "Ashita Moshi Kimi ga Kowaretemo"
• "Break Your Spell"
• "Legendary"
• "Drawing Days"
• "Through The Night"
• "Mezase Pokemon Master"
• "Kimi ni Kono Koe ga"
• "HIT IN THE USA"
• "YOUTHFUL"
• "Hold Me Now"
• "Just One Life"
• "Q-vism"
• "Magi"
• "Fuyu no Hanashi"
• "My Soul Your Beats"
• "High Jump No Limit" and "Joker Almighty"
• "Monster Generation" and "Wish Voyage"
• "Breakthrough" and "Infinite Star"
• "Mankai Kaika Sengen"
• "The Dragon Knights"
• "BRIGHT BURNING SHOUT"
• "Roll the Dice"
• "Yume no Hero"
• "Imperfect"
• "Take Me Higher"
• "Spirit"
• "Ultraman Geed"
• "Goshouwa Kudasai Ware no Na wo!"
• "Trigger"
• "Bokura no Spectra"
• "Kamen Rider BLACK"
• "Kamen Rider BLACK RX"
• "Kamen Rider Kuuga!"
• "Believe Yourself"
• "Justiφ's"
• "ELEMENTS"
• "Bright! our Future"
• "Shooting Star"
• "SURPRISE-DRIVE"
• "Re-Ray"
• "Over "Quartzer""
• "REAL×EYEZ"
• "Another Daybreak"
• "AI ∴ All Imagination Type-02"
• "Dengeki Sentai Changeman"
• "Hikari Sentai Maskman"
• "Choujin Sentai Jetman"
• "Kyoryu Sentai Zyuranger"
• "Tokusou Sentai Dekaranger"
• "Boukensha ON THE ROAD"
• "Kaizoku Sentai Gokaiger"
• "Busters Ready Go!"
• "LUCKY STAR"
• "Kishiryu Sentai Ryusoulger"
• "Tokimeki Experience" "Kizuna Music" and "Initial"
• "Teardrops", "Star Beat" & "Hashiri Hajimeta Bakari no Kimi ni"
• "Live for Life: Ōkamitachi no Yoru"
• "Virtual to Live" & "Hito Yori Jozu Ni" / "Better Than Someone Else" by Yumeoi Kakeru
• "Re:Hello world" by Rikka
• "Night of Summer Side"
• "HEART OF SWORD -Yoakemae-"
• "Hitori no Yoru"
• "Ouka Ranman"
• "Hikari/Simple and Clean"
• "Black Rock Shooter"
• "Kaikai Kitan"
• "Iro Kousui"
• "Kimi no Shiranai Monogatari"
• "Paradise"
• "ODDS＆ENDS"
• "Dragon Knight"^note By Sekai no Owari

GYROAXIA

• "Catal Rhythm" and "Fantastic Tune"
• "Imagination" and "Fly High"
• "Peace Sign" and "Polaris"
• "Rewrite"
• "Clattanoia"
• "Hybrid Rainbow"
• "Mozaik Role"
• "Burn My Dread"
• "Voice"
• "99%" and "Teardrop"
• "BONDS -Kizuna-" and "LAST TRAIN -Atarashii Asa-"
• "Go Forward"
• "Metal Fight Beyblade"
• "Name of Love"
• "H.T"
• "Hikari Tatsu Ame"
• "Mugenranbushou"
• "Judgement" and "Baka Mitai"
• "Just For Myself"
• "Feel Your Noise"
• "Summertime Records"
• "Shadow is the Light"
• "Highschool of the Dead"
• "No Boy, No Cry"
• "Stand Proud"
• "D-TecnoLife"
• "Tougenkyou Alien" & "Samurai Heart (Some Like It Hot!)"
• "Goya wa Machiawase"
• "Kimi no Matsu Sekai"
• "Trasn Candy" and "Reason Living"
• "Colors of the Heart"
• "Next Generation"
• "Signal"
• "Invoke"
• "The Back Horn"
• "Rage of Dust"
• "Black Rover" and "JUSTadICE"
• "Sen no Tsubasa"
• "Kibou No Uta"
• "Rin! Rin! Hi! Hi!"
• "Fighting Gold"
• "Spice of Life"
• "Sight Over The Battle"
• "Eiyuu"
• "Full Force"
• "Break The Chain"
• "Leave All Behind"
• "Armour Zone" and "DIE SET DOWN"
• "Dive into the Mirror"
• "Juken Sentai Gekiranger"
• "Samurai Sentai Shinkenger"
• "Hey-Day Capriccio" and "Tsunagu Soramoyou"
• "Card Of The Future"
• "Karma"
• "Kanzen Kankaku Dreamer"
• "Shinitakunai kara ikitei" / Dying To Live" by Yumeoi Kakeru and "Not For You" by Chronoir
• "Go Go Steel Titan"

Fantôme Iris

• "Itooshii Hito no Tame ni"
• "True Light"
• "Futatsu no Kodou to Akai Tsumi" and "Rinne Rondo de"
• "Midnight Pleasure"
• "Piece of My World"
• "Logos naki World"
• "What's Up People"
• "Kuusou Mesorogii"
• "Shiver"
• "Howling"
• "Hitohira No Hanabira" and "Ranbu no Melody"
• "Guren no Yumiya"
• "Endless Rain"
• "Ma-Ka-Se-Te Tonight"
• "Valentines Eve Nightmare"
• "Sajou no Uta"
• "Netsujou no Spectrum"
• "Believe in My Existence"
• "Falling Roses"
• "Eternal Blaze"
• "The Fourth Avenue Cafe"
• "Kill Real"
• "Into The Madness"
• "Sinful Indulgence"
• "Higurashi no Naku Koro ni"
• "Shiny Tale"
• "Daybreak's Bell"
• "Resonance" and "Black Paper Moon"
• "Re:Re:"
• "Glass Doll"
• "Brave Jewel", "Safe and Sound", and "FIRE BIRD"
• "BLACK SHOUT", "Neo-Aspect", "Song I am"
• "prayer[s]"
• "Hacking To The Gate"
• "Fatima"
• "Redemption"
• "Legend of Galaxy ~Ginga no Hasha~"
• "Kamen Rider AGITO"
• "Supernova"
• "Journey Through The Decade"
• "The Next Decade"
• "Time Judge All"
• "Did you see the sunrise?"
• "Miss Unlimited"
• "One Reason"
• "Ijime, Dame, Zettai" & "Karate"
• "The Invisible Wall" & "UGLY"
• "Within" by Kagami Hayato & "Mitsu no Aji" by Rain Drops
• "Dead Line Circus"

Fujin RIZING!

• "Sugar Song to Bitter Step"
• "K2G"
• "Happy Summer Wedding"
• "Oresama☆Natsu Summer" and "Rakuen Oasis"
• "Theme of Lupin"
• "Nobody's Like Lupin"
• "Tank"
• "Guns & Roses"
• "Deal With The Devil"
• "Flyers"
• "Zettai Muteki☆Fallin' Love"
• "Go My Way"
• "Tsuki to, Hoshi to, Maboroshi to"
• "Wake Up! Decker"
• "Anything Goes"
• "Life Is SHOW TIME"
• "Just Live More"
• "Warera Omou, Yue ni Warera Ari"
• "ALMIGHTY ~ Kamen no Yakusoku" and "Kamen Rider Saber"
• "Taju Roko"
• "SPARK"
• "Choushinsei Flashman"
• "Choujuu Sentai Liveman"
• "Kousoku Sentai Turboranger"
• "Gekisou Sentai Carranger"
• "Engine Sentai Go-onger"
• "Vamola! Kyoryuger"
• "Byun Byun, ToQger"
• "Zenryoku Zenkai! Zenkaiger"
• "Kiyoku Tadashiku Kabutack"
• "Fantastic Dreamer" and "Tommorrow"
• "Himawari no Yakusoku"
• "Maware! Setsugetsuka"
• "Run! Run! Run!", "Bon Voyage", and "We Go!"
• "Distance" and "I Can Hear"
• "Mysterious Magic" and "Hajimari no Sora"
• "Kaisei Joshou Hallelujah"
• "JOJO - Sono Chi no Sadame"
• "Crazy Noisy Bizarre Town" and "Great Days"
• "Kiss You" & "Life"
• "Q&A Recital"
• "Someone Else"
• "Days"
• "Swinging"
• "Mission! Health Comes First"
• "Love Dramatic" and "Daddy Daddy Do"
• "Last Dance"
• "Uchuu no Kioku"
• "Usurahi Shinjuu"
• "Knights the Phantom Thief" and "No Usagi no March"
• "Re-Raise"
• "Nevermore"
• "Beneath The Mask"
• "Egao no Orchestra" and "Kimi ga Inakucha"
• "Taiyou Iwaku Moeyo Chaos"
• "Adrenaline!!!"
• "Fly Me To The Moon"
• "Tsumasaki"
• "Go! Go! Maniac"
• "Rakuen Toshi"
• "Dance Robot Dance"
• ''Memeshikute'' by Golden Bomber
• "Maple Dancer" by Higuchi Kaede

εpsilonΦ

• "Days"
• "Wild Challenger"
• "Red Fraction"
• "Eiyuu: Unmei no Uta"
• "Homework ga Owaranai"
• "Sobakasu" and "1/2"
• "Just Communication"
• "Ignited"
• "Hatena"
• "Splash Free" & "Future Fish"
• "Be My Steady"
• "Kakusei"
• "Longing Freesia"
• "Believe x Believe"
• "Zankoku na Tenshi no These"
• "Can You Feel The Sunshine?"
• "2winkle Star Beat"
• "GARO ~Savior In The Dark~"
• "Ultraman Dyna"
• "Alive a Life"
• "Round ZERO~BLADE BRAVE"
• "Next Level"
• "Climax Jump"
• "W-B-X ~W-Boiled Extreme~"
• "Cosmic Mind"
• "EXCITE"
• "Be The One"
• "Gatcha Goseiger"
• "ADAMAS"
• "Trust Me"
• "Straight Jet"
• "Online Game Addicts Sprechchor"
• "Change"
• "Jinzou Enemy"
• "Love Addiction"
• "Abnomalized"
• "Coolest"
• "God Only Knows"
• "Blizzard"
• "Gakuten Winner"
• "Kaen"
• "Saisei -rebuild-"
• "Kimi no Kioku"
• "Daybreak Interlude"
• "Gamers High"
• "Solider In The Shadow"
• "R.I.O.T" and "EXPOSE 'Burn out!!!'"
• "Unstoppable"
• "Gekidou"
• "Ready Smile"
• "Play Sound"
• "Flat"
• "Love Survivor"
• "Kaze no Kitte"
• "Daia no Hana"
• "Northern Lights"
• "Bang"
• "Let It Burn" by Chronoir featuring Kagami Hayato & "Ukiyo no Enbu" by VΔLZ
• "Higai Mousou Keitai Joshi"
• "Monster"

Inter-band collaborations

• "CHEMY×STORY" by Argonavis featuring Nayuta Asahi