Sadako sits next to 4 phonetic neighbors — Sadako, Sada, and Kazuko are the closest matches by sound. Most share Sadako's Japanese cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"upright child; righteous child"
"renowned warrior"
"of silver, silvery"
"bright, shining one"
"from Lucena, city of light"
"rose, flower"
"alder tree, from the alder grove"
"the third month, heralding spring"
"lily, rose"
"from the kingdom of Lothar, from the Lorraine region"
"lion-like"
"from Denzell (estate in Cornwall)"
"One who tends or holds; occupational name related to tenner"
Similar sound: These names share phonetic patterns with Sadako — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Japanese origins, giving them the same cultural heritage as Sadako.
Rhythm: Sadako is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.