N2 — outside your level filter
fun + to my surprise/regret/delight, X — fronts a reaction word to comment on the clause that follows
tanoshii koto ni
to my surprise/regret/delight, X — fronts a reaction word to comment on the clause that follows
驚いたことに、彼は試験に一発で合格した。
odoroita koto ni, kare wa shiken ni ippatsu de goukaku shita.
To my surprise, he passed the exam on his very first try. neutral
意外なことに、あいつ、ちゃんと約束守ったんだよ。
igai na koto ni, aitsu, chanto yakusoku mamotta n da yo.
Surprisingly, that guy actually kept his promise! casual