menswear for japanese christian wedding?

What do I wear to a christian wedding in japan of two japanese friends?
I have a dark blue pinstripe suit that I wore to a job interview but I am worried that pinstripe is to businessy looking. So I have 3 options. 1. wear the pinstripe, 2. buy something at muji or zara tonight or 3. rental?
Im also wondering as its a summer wedding would it be rude to go without a suit? say a jacket and trousers or no jacket perhaps just a waistcoat or something. The groom and I are both designers and its in omotesando so guess its ok to be a little less conservative? wedding is tomorrow, (July 31st) so quick response would be appreciated. Thanks!

Your suit is fine. Enjoy.

thanks also what about summer wear, can I get away with no suit in japanese summer wedding? any advice appreciated

You will find that even though it is stinking hot, other guests will wear suits. Just put your jacket on when necessary. Being indoors though it isn't hot so you should be fine.

You could buy a summer suit. The material is much thinner and makes a very big difference. They are sold at any suit store, especially this time of year.

@Smoke

thanks! thats helpful didint know that!
( Oh the spammers been deleted in case you all think Im mad.)