Going from Korean to Swahili (Kiswahili) has a composite linguistic distance of 82% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Hangul → Latin
Koreanic ↔ Niger-Congo
The 5 languages with the lowest linguistic distance from Korean:
A quick 3-question check between Korean and Swahili. No signup.