Question about leaving japan and stuff to do

(English is not my first language so excuse the mistakes…)
So i might have to leave japan between soon and the beginning of next year and i have a few questions i would like to ask

-concerning resident taxes, i came to japan in February 2023 so just a bit more than a year, i’m currently employed as a 正社員 so i guess the tax will be deducted from my salary ? But what about the remaining of it or the part for this year if i have to leave japan before the end of the year (or soon next year) ? Can i pay it in advance ?

-about pension, as i don’t know if i will come to japan again for something else than traveling in the future, what will happened to the money that was supposed to be for my pension ? Will i see it again or can i forget about it ?

-do i need to officially close my bank account before leaving ? How am i supposed to pay for taxes and stuff if i have to close it ?

-if i leave, i will have to sell my bike too, what are the steps needed for that ? (Who do i need to tell so that the name registered on it can change,…)

-do i need to go to the townhall to tell them i’m leaving ? Or to tell the immigration?

That’s all the questions i can think as of now but if you have any other advices, it would be more than welcome 🙏