Of course there are thousands of florists in Japan and also it is common to give flowers to friends, family members, relatives and other love ones. Then, it is also normal to give flowers to friends and other close ones when the friend is having a concert or other exhibition in Japan.
However, not like handing over the flowers to your friend directly after the performances, it is very popular to ask the florists to deliver the flowers to the designated addresses.
For example, your friend is having a piano concert in Osaka but you cannot attend it. In this case, you can order the flower online. Then, the florist will send the flower to the concert hall by courier or the local florist in Osaka will deliver directly to the concert hall.
By the way, it is also common to send a flower to your friend who is opening a restaurant or a shop.