Hokkaido: Rebun and Rishiri

Hi,
I'm currently working on my Hokkaido trip in summer and I'm struggling a bit with Rebun and Rishiri.

I will spend one day on Rishiri and stay overnight to leave for Rebun the next morning. I'll stay in Rebun almost all day long and take the last ferry back to Wakkanai.

I was wondering how to get around on both islands. I heard that for Rishiri electric bicycles are a good way. Will I have enough time if I use a bicycle?

On Rebun it seems that a rental car is the way to go, but online I couldn't find any available cars. I'll try and call some companies to see if there are still cars available.

I've seen short bus tours are available as well: http://www.soyabus.co.jp/teikan.htm

But will they give one enough time to really explore the island?

I hope someone who has been there can tell me what the best way of transportation for both islands is and what I should do / see if I only have 1 day for each island.

Thank you. :)

I have been to Rebun only once (never been to Rishiri, though I saw it closely from the ferry). It was more than 30 years ago when a night train from Sapporo to Wakkanai was running. I hopped on the train (I remember it was 21:00 or so) for free because I had a Hokkaido Shuuyuuken ticket. With this ticket we could get on all trains within Hokkaido for 20 days.

I arrived at Wakkanai at around 6:00 and I walked to the ferry terminal to go to Rebun. The ferry arrived at 10:00 or so and I was caught by a woman working for a Minshuku. I dropped off my luggage and a staff of the Minshuku drove me to some scenic place (Maybe Momoiwa-now you can not go there). Then I took a bus to Sukoton and walked to Sukai (sky) misaki. I think it took 2 hours walking. It was a fine day and I enjoyed very much.

The tour bus is only three hours, but it will take you to Sukoton, Sukai and Momodai-Nekodai which are the "must visit" observatories in Rebun. Of course you might better travel by yourself, preferably by walking, but the success very deeply depends on the weather. Therefore, if you are lucky enough to get a good weather, you can see most beautiful part of Rebun within 3 hours tour.

Thanks a lot.
I was able to book a bus tour for both, Rishiri and Rebun. On Rishiri I will have enough time to explore the island on a bicylce as well.
On Rebun I'll have about 4h before the bus tour starts, so I'll try to figure out what to do then. :)

I also need to find out if there's a way to get dinner somewhere on Rishiri as my accommodation doesn't offer any.