3 days to spare. Where to go?

I booked a 27 day trip to japan from late March - mid April. So far, I�fm already booked for
Osaka
Kyoto
Hiroshima / Miya
Fukuoka
Takayama
Tokyo
Nikko

I have about 3.5 days left at the end of my trip coming from nikko. Any suggestions on where to spend them? I am flying out of Osaka but I�fm still open to anywhere near or further from there!

How about getting a closer look of Mt Fuji? Popular places to view Mt Fuji includes, but are not limited to, Fuji Five Lakes area and Hakone.
https://www.japan-guide.com/e/e6900.html
https://www.japan-guide.com/e/e5200.html

Mid April will be cherry blossom season in Nagano, Matsumoto and Takayama. I would save Takayama for the end of your trip and take the long way from Tokyo to Osaka via Nagano, Matsumoto, Takayama, Shirakawago, and/or Kanazawa.

If everything is set in stone, you could still hit Nagano and Matsumoto on the way back from Nikko and then take train from Matsumoto to Nagoyo to Osaka.

A few other ideas:
-Chiba prefecture
-Izu Peninsula.
-Shikoku Island
-Head north from Nikko to Aizu and Sendai

a night at Hikone (a little castle town on Lake Biwa) and then the last few days at Nara would also be nice.

@Lazy Pious as always offers a great suggestion. Hikone with it's original castle & museum plus the lovely garden by the castle and Ryotanji would make for a great contrast to Nikko. Also it's not on the main tourist path so will be quieter. Nara is always fabulous

Thanks everyone.. I�fm goinf to check out Nara while I�fm in Kyoto... but so I�fm thinking Hakone and Nagoya or Nagano

Thanks Stan, nice to see someone who likes similar places to us. We finished off our trip earlier this month (Tokyo/lake kawaguchiko/Matsumoto/Kamikochi/Takayama/Hikone/Nara) with those towns, it is a really nice way to leave Japan IMO rather than the cities. Hikone had their castle festival on for which we unfortunately couldnt stick around, but it looked great and the castle itself is my favorite. We stayed at the Hikone Castle Resort and Spa which was super nice, we wished we had opted for a second night.

Nara as always was awesome, they have just finished the rebuild of the temple next to the pagoda and there was a light up and lantern festival that was a lot of fun and really pretty, we stayed 2 nights at Nara Hotel which has traditionally been our favorite but unfortunately this time we got stuck in the new wing which reeked of smoke and when I opened the balcony door we nearly got carried off by mossies, then we went for some cocktails to recover and were gassed by about 100 people chuffing away on cigarettes and cigars in the bar/lounge, so we ended up being stuck outside on the deck where it was about 10 celsius. All up I'd have to say a big fail from Nara Hotel and after about 5 stays that will be the last time we will go and I really couldnt recommend it again unless you love the smell of stale tobacco.

Luckily we finished off in a ryokan in the forest near Mt Wakakasayama (sp?) whichwas incredible.

Even just the whole Shiga/Otsu/Biwako area. Nagahama has a small castle and museums and shopping district. Ferry ride out to a temple on a small island. Same island can be reached from Hikone. LAke cruises and all the unknown and less frequented (by foreign tourists) temples along the Ishiyama-Sakamoto train line. Even all the beaches along the northern shorelines are worth a stop for lunch and a nice rest midday.

Try more place in Kyushu, like Beppu or Kumamoto. Or if you`re in the Kansai area, check out some smaller spots like Arima hot springs. What about Shirakawago? Just some ideas.

Check out https://www.go-a2b.com/ for cool tips, awesome places, and some best kept secrets in Japan. It really helped me plan my trip.

Adding a day or 2 for Kanazawa would be a good idea.

If you want day trips from Tokyo, there is no shortage - Hakone, the Fuji 5 Lakes area, Karuizawa, Kusatsu, Izu, Kamamura/Enoshima, Kawagoe, Takao, Okutama, Yokohama, the Ushiku Great Buddha, Nokogiriyama, Minakami, Showa Kinen Park, and more.

Adding an extra day or 2 for Kyushu is not a bad idea either if you're going down there. Fukuoka has a number of places you could see.
http://www.thejapanfaq.com/fukpic.html
http://bit.ly/1KAm8cU

But if you can fit it in, Nagasaki would make a great visit.
http://bit.ly/2ob4u8i