[4] Before the band had moved to Tokyo in the spring of 2009, the song "Adventure" was originally planned to be the leading single from the album, in the place of "Sen to Rei".

[11] "Sen to Rei" is a song recorded in common time, with a major key of E and set at a tempo of 132 beats per minute.

[12] The final stanza of the lyrics discusses spatial dimensions: how "on the other side of 1000 and 0, and lines and points" he is a layered world, connecting him to another person.

[8] He based his lyrics on his ideas of what four-dimensional space would be like, considering the fourth dimension to be imagination running inside minds.

[7][8] "Modokashii Hibi" featured aspects of the band's sound that were not present in "Sen to Rei" that they wanted to show off to new listeners.

Part way through recording, the bucket's handle broke off, and this sound as well as Iwadera laughing were included in the final mix of the song.

[1][22] The song is a frequent part of Sakanaction's live concert sets, and live recordings of the song have been released by the band six times: in the bonus track on the "Aruku Around" (2010) single featuring audio of three songs from the Sakanaquarium 2009 concert in Sapporo, twice on their Sanakaquarium 2010 DVD set, as performed at the Kikuuiki tour final at the Shinkiba Studio Coast on May 15, 2010 and at their Nippon Budokan concert on October 8, 2010, as well as on their Sakanaquarium 2011 video album, Sakanaquarium 2012 "Zepp Alive" digital live album and their Sakanatribe 2014 video album releases.

Toyoda was inspired to create the video after hearing of the song's themes, and depicted the band travelling from the first to the fourth dimension.

Yamaguchi asked Toyoda to specifically emphasize the rock and human aspects of the song and the band, rather than the electronic sound.

[13] CDJournal reviewers felt "Sen to Rei" expressed loneliness, and praised the new Sakanaction-style guitar rock, as well as their ever-changing style.

The reviewers were impressed with Yamaguchi's chorus vocals, which changed from "subtle and tender to hopeful and empowered", and called the song a "fast-paced killer tune".

[28] Reviewing the single as a whole, Okazaki described the B-sides as having "room temperature dance beats", and felt that they sounded fresh, in comparison to the highly powered "Sen to Rei".