Of course! Here are some travel tips for your ventures to Fukuoka, Beppu, Yufuin, and Nagasaki:

Best Time to Visit:
The best time to visit would be late March to early April for the cherry blossoms, or October to November for the autumn leaves. Summer months can be hot and humid, and winters are generally mild.

Route and Accessibility:
Access to these areas is quite easy with Japan's well-connected train system. From Fukuoka, you can take a train to Beppu (Oita), which takes around 2 hours. From Beppu, Yufuin is less than an hour away by train. Lastly, to reach Nagasaki from Yufuin, it would require a transfer at Hakata (Fukuoka), totaling around 3 hours.

Altitude and Acclimatization:
All these places are more or less at sea level, so there aren’t significant issues regarding altitude and acclimatization.

Accommodation and Booking:
It's advisable to book accommodations in advance, particularly if you aim to stay in a ryokan (traditional Japanese inn) or during peak travel seasons. Onsen towns like Beppu and Yufuin can get rather busy during these seasons.

Clothing and Essentials:
Pack lightweight, comfortable clothing for the summer, and multiple layers for cooler weather. Be sure to bring comfortable walking shoes. An umbrella or raincoat could be helpful as there could be sudden showers.

Health and Safety:
Japan has an excellent healthcare system. However, residents and tourists should have their own insurance as medical fees can be expensive. Tap water in Japan is safe to drink, and food safety standards are high.

Local Etiquette and Respect:
Japanese culture values respect and manners. Be mindful of local customs such as being punctual, removing shoes before entering certain places, and avoiding loud conversations in public areas. When visiting shrines or temples, observe respectful behavior and dress appropriately.