ともに after a unit of time?

Question

I came across these lines in a song (0:59):

十日ともに

投げた賽は

赤く色づいた

As far as I know, ともに means something like "together with," but "together with ten days" doesn't really make much sense.

There's also the less common meaning "both," but again, "both the 10th/ten days, and the die I cast, turned red" doesn't make much sense either.

Am I misinterpreting this? What's going on here?

Answer 1

The speaker is referring to how s/he and another person cast the die together over a period of 10 days. The あなたと is omitted.