The twenty-ninth ending song for the manga adapted anime series, Bleach.

Originally released on December 14, 2011, along with “寂しくて眠れない夜は” (Sabishikute Nemurenai Yoru wa) and “Poker Face.” Later included in Aimer’s first studio album, Sleepless Nights.

The song explains that a person couldn’t live for the sake of the partner. So, they split up. This person prayed to be able to forgive his/her own selfishness and also to live without regretting not having carried on that relationship. She/he believes that by doing so, one will become stronger.

“Re: pray” has two explanations.
It is a reply to a pray as “re:” is used to forward an email received previously, and “pray” is the subject. This is an evocation of the past, so it is a reminder of the aim of breaking that relationship.
The second one is “re-pray” where “re” is a prefix that means “again”. Therefore, it means pray again. This person is still hoping for a better future without her/his former partner.