Riding bike in the rain

What is the preferred method for high schoolers of covering up themselves and a boxy backpack when they have to ride their bike in heavy rain to catch the train to go to school? I want to be prepared for what to do when the rainy season comes.

I saw some sort of wider plastic-raincapes there, that covers the upper half of you, your backpack and your bike.
I think they would be available everywhere or in some bicicle shops at least.

Greetings,
Vio

Poncho
Umbrella
Nothing at all

Are essential the 3 widely used options

Or walking with umbrella

Unlike places like Hanoi in the early '90s, high school students in Japanese cities don't typically ride bicycles in rain. They either walk or take a bus. You should discuss it with your school or your neighbors-to-be to see what's commonly accepted in your district.

Rain or not, but especially when raining:
Use a flashing tail light (some helmets have this feature).

I would just get one of those large ponchos for rain that goes over the bag and person. It's much easier to deal with instead of worrying about holding an umbrella. Besides, technically to Japanese law, you're not allowed to hold an umbrella while riding a bike as it's deemed as dangerous.