as for this; this (topic)
Used to introduce or emphasize the current topic, often at the beginning of a statement. Equivalent to これ + topic marker は.
This is my book.
This is an important issue.
Interjection expressing surprise or drawing attention when encountering something unexpected. Often used in casual speech; compare with こりゃ.
See also: こりゃ
Well, I'm surprised!
Well, well, long time no see.