-기로서니
granted that …, (still how could)
5-daraja · Bogʻlovchi
Izoh
Grants the first clause but says it doesn't justify the second; the main clause is often a reproachful rhetorical question. Attaches to the stem; past -았/었기로서니; often with 아무리.
Misollar
아무리 바쁘기로서니 전화 한 통도 못 해요?
However busy you are, you can't make one phone call?
화가 났기로서니 물건을 던지면 되겠어요?
Angry or not, is it okay to throw things?
어리기로서니 그런 행동은 용서할 수 없다.
Young as he is, such behaviour can't be excused.
TOPIK izohi
TOPIK II Reading 46–47 (critical attitude).