Sasuga (さすが) means “just as you'd expect”: praise for someone who has lived up to their reputation, like “that's so you!” or “no wonder!”.
A character pulls off something impressive, and someone breathes さすが…. The subtitles say “amazing,” but that misses the flavour. さすが is praise WITH HISTORY: “this is exactly what I expected from you — because you're you.”
How to use it
On its own — さすが！ — it works like “nice one!” between friends. The unspoken second half is always “…living up to your reputation.” That's why it lands harder than a plain すごい.
この かんじ、 よめますよ。
I can read this kanji, you know.
さすが ゆきさん！
That's our Yuki!
The twist: さすがに
Add に and the mood flips. さすがに means “even so, there is a limit / that really is too much” — a limit has been reached.
When someone says it to you
The classic modest reply is いえいえ (“oh, not at all”), waving the praise away. A simple ありがとうございます is fine too, and it never sounds wrong.