Koi sits next to 3 phonetic neighbors — Kai, Coy, and Roy are the closest matches by sound. Most share Koi's Japanese cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"love, romantic feeling"
"garden of God, orchard"
"poet, bard"
"the kingdom of Ciar, County Kerry"
"powerful ruler"
"creative phonetic variant of Kaizen"
"variant of Devon: from the Devon region"
"second of twins"
"knight, mounted warrior"
"huntsman, game warden"
"firebrand meadow, sword clearing"
"crow crossing"
"blessed one"
"intelligent, wise"
"God is my justice"
"son of grace; graceful"
"honoring God"
"Greece, land of wine"
"place by a waterway lock"
"small"
"little slender one"
Similar sound: These names share phonetic patterns with Koi — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Japanese origins, giving them the same cultural heritage as Koi.
Rhythm: Koi is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.