Daycare has become very good in Japan (I don't know about the rural areas). Many cities are trying their best to accommodate all the children so the parents can keep working if they please. I think the government is putting pressure on cities because of declining birth rates to be as helpful as possible. Where I live you can put your child in daycare starting at 4 months with special exceptions (low income so both parents need to work, etc), or starting at 1 year old for regular folks. It's a little difficult to get into your choice school usually but they can usually fit you in one of your top three choices.
> Daycare has become very good in Japan (I don't know about the rural areas)
As you mentioned, don't generalize to everywhere in Japan. I can tell you even in Kansai it's far from ideal and the daycare facilities are completely full and you need to reserve more than a year in advance to even have a chance to get your kid in.
Okay I made a mistype. Daycare has become much better is the correct thing to say. It's not the best but much better than it was 15 years ago. There is a "waiting list" almost everywhere I know of but if you try you can get in generally.
I was unable to get my son (8 months old at the time) into daycare anywhere near my home in southern Tokyo; we were lucky to get into a private place four stations in the opposite direction of my workplace.
This was last year. The situation is very much still problematic, even in cities.
You don't always have a choice - because there are no or few daycare facilities available anyway, and you may not live close to your parents either.