This song was recorded throughout late September 2010 and recording completed on October 2, 2010. Shuhei Naruse is the song's producer and it is sung by Shu Watanabe under the name of his character Eiji Hino.
It was first used in the October 3, 2010, episode. The pronunciation of "Tighten Up" is intended to mimic the pronunciation of "Tatoba". When played during scenes with other Combos, the "Tatoba" chant is removed from the song. The single for "Regret nothing ~Tighten Up~" features a ska arrangement by trombone player Eijiro Nakagawa.
Erai hito mo tsuyoi hito mo
Otona ni natte mo
Zettai katenai hazu
Kako ni yoi dekita kuyashisani
Yuuki areba fumi kometanara
Kono kokoro no kizuato
Jikan dake wa mou motosenai
Hito no sei ni mo dekinai sono kioku Can't delete
Nani mo kamo jibun toiu unmei no naka
Kowaku te mo herahera warau na
Dare no tame nante yuutsumori mo nakute
Saidaigen doryoku shita shiru shiwo I can go nowhere nokosu shikanai to shinjiteru
Jibun wa mou azamuku na Regret nothing!
Hateshinaku tsuzuku ashita no tame ni dare mo
Junbi shite iru sore wa honto ni hitsuyou?
Me ni mieru mono takusan atsumete mite mo
Yaku ni tatanai hora sore yori koukai shinai
Tsuyosa wo mote tsumari... Regret nothing!
Me no mae de keshisarare sou na hikari ga
Aru no nara kono te de mamoritai I can go nowhere nigedaseru basho wa nainda
Mukiatte tatakau beki Regret nothing~!
Even great people, and strong people
Even if you grow up
There’s no guarantee of winning
Against the frustration that has been left from the past
If you have courage, when you are stuck
You can get off with ignorance
This scar in the heart
Can only not bring back time
Unable to blame it on others, you can’t delete that memory
Everything is within the fate of yourself
Even if you’re afraid, just grin widely
I don’t plan to say something like “it’s the proof that
I’ve done my best for the sake of someone”
I can go nowhere; I believe I can only remain
And stop fooling myself, regret nothing!
For the unending, continuing tomorrow, everyone
Is preparing; is ‘that’ really necessary?
Even if you gather many things you see with your eyes
They aren’t useful; instead, have the strength
To not regret; in other words… regret nothing!
If there is a light seeming to be extinguished
In front of me, I want to protect it with these hands
I can go nowhere; I don’t have a place to escape to
I have to face it and fight, regret nothing!