The script utilizes homonym confusion about the character name Baku, the pronunciation of which is used for three different meanings:
- a mythological creature that is said to eat up nightmares, which Haruyo alludes to when she first appears in a yakiniku bar
- cereal crops like wheat or barley except for rice, which the kanji for the character name refers to, the same usage as in the title name "Bakushû" (Early Summer, or literally, "Barley Autumn") by Yasujirô Ozu
- the animal tapir, when Ryôhei talks about the zoo and searches images on the smartphone.
In the original Japanese language, all characters speak dialects of their supposed home regions (Osaka, Tokyo, and Tohoku) regardless of the actors/actresses' real native tongues. Masahiro Higashide, among others, speaks both Osaka dialect as Ryôhei and standard Japanese (of Tokyo) as Baku.
The first commercially produced film directed by Ryûsuke Hamaguchi.
In the original novel by Tomoka Shibasaki, Asako associates the names of Baku (wheat) and his sister Mai (rice) with those of siblings River, Rain, and Summer Phoenix, finding a similarity in kind of nature-oriented way of naming them. Although the film version makes no direct mention of Phoenix siblings, all three (rivers, rain, and summers, as each word literally means) make up distinct elements of the film with more emphasis than in the original story. (As for summers, the first Tokyo sequence until the Tohoku Earthquake of March 2011 is exceptionally set in winter based on real history.)
The original title in Japanese ("Netemo sametemo") translates literally as "asleep and awake," an idiomatic expression that roughly means "night and day," used often associated with love-sickness. Some dialogues in the film reflect this literal meaning of the title.