Cheapest but still relatively safe airline to go to japan?

I am a student and am travelling with a group of friends to Japan during the December holidays. Right now we are looking at SQ, Scoot, JAL and ANA etc. which are all 800 to 1k+

But we found zipair and japan air, which we heard are budget friendly. However, the thing is they have not opened booking for December(they are greyed out, unless they are already completely sold out somehow?)

Any advice is appreciated, or any alternatives too

Should we take the risk and not book now and only when the two airlines are available or play it safe and book now?