Medium size luggage at Takamatsu

I will be staying in Takamatsu for 3-4 days, using it as a base to explore the Seto Inland Sea islands as well as the city itself. I am planning to arrive at Takamatsu from Onomichi early in the morning on the 1st day. If possible, I hope to go catch the first ferry to Megijima immediately when I arrive at Takamatsu, hence I won't have time to check in to the hostel where I'm staying since I need to use the electrical railway to get there.

I've looked at various websites, and while there are lockers at Takamatsu Station they seem to be too small for my medium size suitcase. I am also aware that there is a luggage drop counter at the Station, but it closes at around 5:30 pm, but I'm not sure whether I will return from Megijima/Ogijima in time without rushing my travelling.

Are there any other luggage storage options near Takamatsu Station or Takamatsu Port?

Actually, there are big coin lockers in Takamatsu station, so you should be able to store your luggage there:
http://takamatsulife.com/blog/2015/11/25/takamatsu-station/

I used one of these last summer....

You might also check out this link for more coin lockers in Takamatsu city :
http://takamatsulife.com/blog/2016/11/11/coin-lockers-takamatsu-city-c...

medium, large all available :
http://locker1.exblog.jp/20233908/

As Logan and "guest" have responded, you will most likely find what you need at Takamatsu Station if your luggage is regular size.

However, how will you get to your lodging? By JR train or by Kotoden train?
If it's JR by all means, use Takamatsu Station's lockers.
However, if you're going there by Kotoden, you may want to leave your baggage in the port lockers or in Takamatsu-Chikko Station lockers.
This way you won't have to return to the JR Station.

The port lockers are outside this building and some are pretty big: https://goo.gl/maps/J53uHaFBVDv
The Kotoden station (Takamatsu-chikko) is here: https://goo.gl/maps/ARJspMY8ue92
(one caveat, I'm not too sure how big the lockers are there).

Depending on what train you'll take to reach your hotel, and what time you'll arrive in Takamatsu in the first place, those are your options.

In terms of schedule, Meon (Megijima - Ogijima ferry) leaves at every "even hour" (8am, 10am, 12pm, etc), and when returning, you'll most likely arrive in Takamatsu at 5.40pm.

Another advice if you spend the day on both islands: plan more time on Ogijima than Megijima (if you take the 10am boat, I'd say spend no more than two hours on Megi, and then take the 12.20pm boat to Ogi and stay there until 5pm).

If you need more advice about the area and the islands, do not hesitate to ask. :-)
You can also check my site, I'm not sure if it's OK to link here or if it'll be considered as spamming, so just google my nickname (with appropriate spaces) you should find it easily. :-)

Thank you all for your information! I've decided though to check-in at Takamatsu in the evening before exploring the islands the next day - it's quite a rush getting from Onomichi to Takamatsu in the morning, after all.

Re DavidSetouchiExplorer, I've browsed your website, certainly it's getting me more excited about my upcoming trip! Since you seem to have experience exploring the islands, wonder if you can help out with my questions:-
1. I am planning to catch the 10:00 ferry from Takamatsu to Megijima/Ogijima. I note your comment that I should plan more time at Ogijima. Is there any particular reason why? My original plan was to arrive at Ogijima first at 10:40, explore and then board the 1:00 ferry to Megijima.

2. I'm actually planning to visit Teshima and Inujima (from Takamatsu) on a separate day. My plan is to arrive at Inujima at 10:15 (via ferry, passing Naoshima and Teshima), and then catch the ferry departing Inujima at 1:00 to Teshima. My thinking is that the art sights at Teshima are more spread out compared to Inujima, and I expect the queue at Teshima Art Museum will take quite a while. Is this reasonable, or will it be too rushed to fit two islands into one day?

3. Did you happen to try the Kishun (�S�{) restaurant at Megijima? Is it any good?

You're very welcome, and thanks for checking out my site. :-)
Yes, arriving in Takamatsu in the evening will probably make your life easier.

1. The reason I'm advising you to spend more time on Ogijima than Megijima is because Ogijima is a much more interesting island. In all honesty, Megijima is mostly "Takamatsu Beach", but off season, there isn't really much to do or to see on the island (do not spend time and money going to the cave unless you have kids). On the other hand, Ogijima is probably the cutest island in the region, the village is simply beautiful, if you decide to walk around the island, you'll have a great experience of the Seto Inland Sea (OK, you can do that on Megi too). The people are super nice and welcoming. It is also the success story of the area in terms of island revitalization (population has grown steadily for the past three years, something unique in Japan) and all the young blood is bringing a great energy to the island (go check the library).
I can spend days on Ogijima (oh wait, I do... I go there once a month, at least), while a yearly trip to Megijima is more than enough.
And of course, there's the art (be careful, it's open only on week-ends on both islands), but even the art is more interesting on Ogijima than Megijima (Ogijima's Soul, Onba Factory, Memory Bottles, Akinorium and the Room inside of the Room are some of the best artworks of the whole area). On Megijima, the Island Theatre, MECON, the Presence of Absence and Equipoise are not to be missed.

So, my advice would be take the 10am ferry to Megijima, stay there until 12.20pm (two hours is enough time to visit the art, walk around the village and along the beach a little) and then stay on Ogijima for the rest of the day (visit the art, get lost in the village, hang out at the library and Onba Café, etc.)

2. Visiting Inujima and Teshima in one day is not very realistic. Inujima can be visited in two hours, but Teshima is closer to one day and a half. :-)
Now with that being said, I've done what you're planning: Inujima in the morning, then arriving to Teshima at 1.30ish and visit parts of the island for the rest of the day. If you limit your visit of Teshima to only on part of the island (let's say Karato, where the Art Museum and Shima Kitchen are) you can do it, and you can have an interesting experience. Just don't expect to visit all of the island. If you don't mind returning to Takamatsu late, when you're in Karato, instead of having to return to Ieura to catch the last boat to Takamatsu, you can take the ferry from Karato-hama to Shodoshima and then from Shodoshima to Takamatsu. The price won't be very different, but it'll take almost two hours instead of 35 minutes. However, it may allow you to visit more art on Teshima (you won't have to go Ieura-Karato-Ieura, just Ieura and then Karato).

3. You mean Umiyado? I never ate there, but I heard very good things, and the owners are very nice. However, if you decide to follow my advice, you may not have the time to have lunch on Megijima. In that case, may I advise you to have lunch at the Library on Ogijima, or at Bistro Iori.

Once again, I hope that helps. And do not hesitate to ask more (just this forum doesn't send e-mail notification, so I may forget to check it out in a timely fashion - the other option is to contact privately from my website).

Best.