I can guarentee there will be a structual wall. The good news is the area where i am rooming walls you can see the framming from outside due to its old building style.(The drywall is between the frames with nothing between them. I may ask a structual engineer from work to come out after i have removed all of the drywall to have him inspect the integrity of the structual beams.(One beam i'm pretty sure i will need to remove or place 2 new ones on each side as its a corner of the storage room. It has some cracks due to drying i beleive when i own the house i'll have a second look at that beam and possibly will post a picture of it here.) Originally i was going to replace all of the wiring throughout the house to but my electrical engineer friend who came out with me looked at it and said its copper and its clean you wont need to replace any of those wires by looking at the breaker box.

Seek local assistance.

Please try to be a bit more detailed I'm not quite getting your full point. I have assistance from fellow coworkers who are engineers of several varieties. Also for things such as plumbing, the breaker box hookup, and possibly that structual timber once i get it looked at.(It may be more once i take the floors and drywall off in the interior. Btw this is not my first time with doing renovations.

We can’t possibly know about Japanese buildings I do know a lot of time they were built with eartquake issues met so you need real info from where you are

Reach out to the ex-pat community in your location. I suspect there will be expertise and experience available.

Ive reached out a few times on reddit and most people out here don't do anything DIY as they run into the same problems i do lack of product informaiton and do not know any real companies in the area.

The only companies in the area are reform companies as i have stated which really do not come out to explain how to do work of course because they want to earn money and the less you know the better it is for them. My initial quote from the reform company to do only the bath area(no cabinets or sinks just floors) and kitchen was about 5million yen which is roughly 45k

-2million yen to install a water heater and remove the old oil heater.(they are still going to remove the old oil heater i'm having a different company install a water heater older model but new)

-floors in bathroom, storage room and removing a plaster wall between the original mini bath area and fix the floor in the storage room for 1 million yen.

-Tiles for bathroom and kitchen about 200k each

-toilet room upstairs for 500k(remove a frame wall destroy a japanese old style toilet adjust piping to conform for new toilet and install new toilet, tiles and sink.(This room is very small btw not like imagine 2 small closets)

-laundry room for 700k.(remove a frame install tile remove sink and urinal.)

-dispose of drywall and wood waste(not urinals, porcelin skins, bathtub, urinal, or toilets each of those is 30k yen)

-220k yen(the incinerary is litterally 10 minutes from that house and they can destroy anything for 150 yen per 10kg.)

-100k yen for a breaker box 20k yen per new outlet to install.

With this said that 5million yen is pretty much getting me nothing and most of it is work that can be done for about 1million yen for contractors to do some of the certified work that has to be done such as electrical, water heater, and plumbing. 1million yen(Materials), some friends, and beer. like i said and anyone who has had their house reformed out here the costs for getting stuff done to your home is extremely high labor costs because normal japanaese are passive and will not argue a price.(They also do not do very much DIY stuff themselves and know nothing about DIY. Lack of knowledge, lack of tools, and lack of time as most japanese work exteme working hours and have no time to do anything but work.) lastly with that 5million yen cost this does not account for any major issues that may come up such as a structual beam needing to be replaced, molded walls or frames, pests, or anything else(overrun costs)

I'm pretty much on my own except for the sales section of the local homes store.(Hardware store very useful here they have alot of supplies.) If you know another site i can toss these questions at i would be glad to hear about it at least then i can find a decent plumber or electrician for a good price.

There are a lot of things that are different about japanese construction vs american but most are the same they use 2x4s, plywood and drywall.(The modern houses do) Electrical wiring, and construction grade building materials are available at homes also. The only things that are not really available are concrete backer boards and waterproofing membrane(I'm still researching this i found they have it for balconies so im sure they have something for the interior.( as i have seen some photos with bathrooms that have it. Also they normally use real concrete here which is going to suck but is not impossible.).

P.S.(there are your paragraphs strategery)