My friend leaned in and curiously asked me what had really happened.

curiously 是形容词 curious 的副词形式，由词根 curi-（关心、注意）和后缀 -ous（形容词后缀）组成，再加上副词后缀 -ly 构成。curious 意思是"好奇的"，curiously 表示"好奇地"，描述询问时的态度和方式。