In the syntax unwrap(x) {x -> } nah {} the nah function naming is not ideal.

I suppose NAH is an acronym for "null a.. h.."? Hm, I have no idea. Anyway, it would read better if it were a natural english word, like unwrap.. or ... Additionally, NAH very strongly resembles a Russian expletive for "go f*** yourself" :(

inline fun <T1, T2, R> unwrap(
        t1: T1?,
        t2: T2?,
        block: (T1, T2) -> R,
        block2: () -> R): R? {
    return if (t1 != null
            && t2 != null) {
        block(t1, t2)
    } else {
        block2()
    }

이런식으로 탔으면 좋겠다 싶을때가 있었는데, 이렇게 만들지 않고 할 수 있는 방법이 있을까요?

I think in Func.kt file you can check variables in more elegant way:

    val hasNull = arrayOf<Any?>(t1, t2).contains(null)
    if (!hasNull) block(t1, t2)
    return Unwrap(valid = !hasNull)

Instead of

    return Unwrap().apply {
        if (t1 != null
                && t2 != null) {
            valid = true
            block(t1, t2)
        }
    }

To do it you should make valid field as constructor parameter. It make your code more readable and maintanable and also allow explicitly specify valid field that is more preferable.