I was looking for a simple anime song piece where I encounter this piece whose first bar does not make sense to me (I uploaded the first bar picture ).
Especially what is meant by 2 and 3 at the top of the first two notes? Is it tuplet or finger indication? 
Thank you.
The 2 is a fingering notation; the 3 is over the middle and in a different font and size, so I can tell that the 3 is the indication to play a triplet (and the measure only adds up for a triplet). So that 3 doesn't necessarily mean to finger the first A with the 3rd finger, though you may wish to.
The notation means:
(This is not super clear upon viewing. Good question!)
The 2 is a fingering indication.
The 3 (which is in italics and a larger font) is indicating that the three notes are a triplet - so the first three notes take one beat.
Hope that helps.
Well, like others said: the font and positioning (and beaming) make clear that the first is a fingering indication and the second is a triplet indication, but...
If I were playing this, I'd rather use a "1" on the first note, then a "3" where the triplet "3" is written. That way you can play a "4" on the B and don't need to change strings for two notes (what's that last A supposed to be? Another "4", making for a lonely "B" on the A string, or "0" making for a two note phrase on the A string?).
As a note aside: it would appear that this is sort of a partitura (since "Violin" is marked and other instruments apparently follow below) which makes it a bit unusual that fingering indications are printed at all.
But a bass figure this clearly ain't.
Those just look like fingering indications, but yes that rhythm only makes sense if it is triplets. Sometimes they go un-notated.
