“Rebirth Theory” is a song created by Utsu-P for the idol group Q'ulle, released on March 1, 2016. The song was later released on the single ALIVE/Saiseiron on May 18, 2016

The lyrics were written by DECO*27 and revolve around the importance of staying true to oneself and pushing through difficult times in order to achieve personal growth and fulfillment.

The music itself is a blend of electronic and metal elements, with a fast-paced beat and catchy melodies. The song features Q'ulle's idols Ikura, Yakko, MANAKO, Maam, and Yuzuki. The video showcases the group's dance and choreography

The song is 3 minutes, 38 seconds long. The first thirteen seconds consist of a synthesizer and a drum-loop, Interspersed is a filtered guitar track. The song then immediately shifts into a heavy guitar riff, which plays continuously throughout the duration of the song. The song contains a catchy, straightforward song structure. Complete with a breakdown and refrain.

Up to the point of this song's release, Q'ulle's song style had mainly stuck within electronic pop or pop rock. Utsu-P's distinctive melody writing and down-tuned guitars offer something jarring to unaccompanied listeners.

A cover by the backing band of Q'ulle was uploaded to niconico douga simultaneously with the original

An instrumental version appears on the limited physical edition of ALIVE/Saiseiron

Q'ulle would perform this song frequently at their concerts, snippets can be seen on live digest videos on their channel.

(Color coded to each singer's solo lines. Ikura, Yakko, MANAKO, Maam, and Yuzuki)

意味のないことに思えたんだ
「昨日」を今日も重ねるのは
飽々していたんだ　同じ僕に
理想は今日も　色を変えて

煙る倦怠感　陰る最上段
あれやこれが火を奪っていく
止まることは許されないよ
僕にはもうこれしかないの

だから

再生論　理想を理想にしないで
散散だって言ってないで　困難だって愛しちゃって
どうせ僕が終わるならば
曖昧なんて信じらんない　体内外削って叶えろ

あ、流れ星！じゃあ私が全員分まとめて言うね
夢が叶いますように夢が叶いますように夢が@^#%!#&^*&….
悲しみ喜び怒りも全部　今日の日を生き抜くためのパートナー
逸れぬように繋ぎ合う手と手　いつだって一緒だって

回る照明が　照らす存在は
苦しみ抱いて　輝きを増すの
藻掻くほどに僕を知るんだ
他の誰にも真似できない

僕を

再生論　過剰で多情になれよ
ヤイヤイ言って尻尾巻いて　わんわん泣いてどうしたんだい
上限イッパイの理想で吠えろ
Hi-Fiハートビート for you　限界だって突破しようぜ

戻れない　鍵穴はまだ見えない
探そうか　ここからまた僕を始めよう

再生論　理想を理想にしないで
散散だって言ってないで　困難だって愛しちゃって
どうせ僕が終わるならば
曖昧なんて信じらんない　体内外削っていこうぜ

再生論　過剰で多情になれよ
ヤイヤイ言って尻尾巻いて　わんわん泣いてどうしたんだい
上限イッパイの理想で吠えろ
Hi-Fiハートビート for you　限界だって突破しようぜ

戻れない　鍵穴はまだ見えない
探そうか　ここからまた僕を始めよう

(Color coded to each singer's solo lines. Ikura, Yakko, MANAKO, Maam, and Yuzuki)

Imi no nai koto ni omoetanda
“kinou” o kyou mo kasaneru no wa
Akiakishiteitanda onaji boku ni
Risou wa kyou mo iro o kaete

Kemuru kentaikan kageru sai joudan
Are ya kore ga hi o ubatteiku
Tomaru koto wa yurusarenaiyo
Boku ni wa mō kore shika naino

Dakara

Saiseiron risou o risou ni shinaide
Sanzan datte ittenaide konnan datte aishichatte
Douse boku ga owarunaraba
Aimai nante shinji ran nai tainaigai kezutte kanaero

Aa, nagareboshi！ Jaa watashi ga zeninbun matomete iune
Yume ga kanaimasu you ni yume ga kanaimasu you ni yume ga @^#%!#&^*&….
Kanashimi yorokobi ikari mo zenbu kyou no hi o ikinuku tame no paatonaa
Hagarenu you ni tsunagiau te to te itsu datte issho datte

Mawaru shoumei ga terasu sonzai wa
Kurushimi daite kagayaki o masuno
Mo kaku hodo ni boku o shiru nda
Ta no dare ni mo manedekinai

Boku o

Saiseiron kajoude tajou ni nareyo
Yai yai itte shippo maite wanwan naite dou shitandai
Jougen ippai no risou de hoero
Hi-Fi haato biito for you genkai datte toppa shiyouze

Modorenai kagi ana wa mada mienai
Sagasou ka koko kara mata boku o hajimeyou

Saiseiron risou o risou ni shinaide
Sanzan datte ittenaide konnan datte aishichatte
Douse boku ga owarunaraba
Aimai nante shinji ran nai tainaigai kezutteikouze

Saiseiron kajoude tajou ni nareyo
Yai yai itte shippo maite wanwan naite dou shita n dai
Jougen ippai no risou de hoero
Hi-Fi haato biito for you genkai datte toppa shiyouze

Modorenai kagi ana wa mada mienai
Sagasou ka koko kara mata boku o hajimeyou

• The music video and it's choreography is referenced in Q'ulle's song ALIVE, appearing on a laptop screen and later as a fan dancing to the song.