The Japanese proverb "Izure Ayame ka Kakitsubata" ("Which is the iris, and which is the water iris?") is used to describe a situation in which several people or things are all so perfect that it is difficult to determine which is superior.
The origin of this proverb is said to come from an episode involving Minamoto no Yorimasa, a military commander of the Heian period. After slaying the legendary monster known as the Nue, he was awarded a beautiful lady named Ayame-no-Mae as a reward. However, as a clever challenge, the retired emperor ordered him to identify her from among twelve women. Troubled by the task, Yorimasa is said to have composed the following poem:
Through the early summer rains,
Across the waters among the marsh reeds,
I hesitate, wondering
Which one is the iris.

This poem is considered the source of the proverb.

This composition is based on flexible quintet instrumentation and can also be performed by ensembles consisting of instruments from the same family, such as clarinets, saxophones, or brass instruments. The work was designed with mixed-instrument ensembles in mind, and careful consideration has been given to the technical difficulty and range of each part.
The Part 1 high woodwind instrument and percussion parts are optional. If only one percussionist is available, the player may combine 1st and 2nd parts as appropriate, performing according to ability and available instruments. For the wind chimes, the choice of octave is left to the performers. Musicians are encouraged to interpret and perform the work in a manner that best suits the character and atmosphere of each section."

(Nozomu Noro)