I buy sections of tubing at local flaps and join together. They have flared fittings on both ends. NO flaring. Find out the lengths they have, draw it out on paper, get as close as you can and give an extra bend here and there to shorten run. Use couplings, elbows, tees, etc. to accomplish. Easy. I have no idea what is available locally in Japan. So may not be best for you.
