Question

japanese haiku are similar to english romantic poems because they both
contain strict rhyme schemes.
include themes about nature.
use a kigo to reveal details
follow a fixed structure.

Explanation:

Haiku is a form of Japanese poetry that follows a fixed structure of 5 - 7 - 5 syllables. English Romantic poems often have a more flexible structure compared to some other forms, but haiku's fixed structure is a key characteristic. Romantic poems don't necessarily have strict rhyme schemes like some traditional forms (e.g., sonnets in a strict Petrarchan or Shakespearean rhyme scheme). While some Romantic poems may touch on nature, it's not the defining similarity here. Also, using a kigo (a season word in haiku) is specific to haiku and not a similarity with English Romantic poems.

Answer:

follow a fixed structure.