I've compared Mr. Children to The Beatles, and if someone asked me for an example, I wouldn't have to go much farther than this song "[es] ~Theme of es~", the band's 8th single from May 1995.
When I listened to the CD single for the first time, I thought that Kazutoshi Sakurai（桜井和寿）and crew were trying to emulate something from The Beatles' more introspective period, post-"Sgt. Pepper's". And although the songs are completely different, I couldn't help but also get reminded of Billy Joel's "Scenes From An Italian Restaurant".
Whatever the inspiration, "[es]" definitely has sweep. Starting with Sakurai and a simple guitar melody in balladeer mode, the song slowly goes into a crescendo as more of the band and an orchestra come in to provide an epic conclusion. The song was used as the theme song for a documentary on Mr. Children so at the time, I hadn't been sure whether Sakurai had wanted to create a ballad to document the history of the band. I was certainly curious as to what the "es" was all about.
I found out from J-Wiki and Wikipedia that the title was the German word for the psychological term "id", that part of a human's personality providing the basic primal drives. And from what I could understand of Sakurai's lyrics, the singer wants to strip himself of all of the fame and accolades and just reveal his true self to the one he loves, to reach true joy. I found a full translation of the song at an English fansite for the band so you can peruse the lyrics there to get that meaning.
The melody has that feeling of a condensed journey so I'm hoping that Sakurai was able to find his rainbow at the end of it. As I mentioned, the lead vocalist was responsible for words and music while producer Takeshi Kobayashi（小林武史）arranged it. "[es]" stayed at No. 1 for a couple of weeks and was the 12th-ranked single for 1995. The song is also included on Mr. Children's 6th album, "Bolero" from March 1997 which also hit No. 1 and was the 2nd-ranked album of the year. In the history of the Oricon charts, it is currently the 14th-ranked album all-time breaking through the 3-million barrier.