Upvote:3
It is strange that the online application system asks your for a proof of relationship, if the person you are visiting is a friend and not a family member nor a spouse. Double check that you have selected the right relationship during the process. In should be this Question 4 on this part of the application:
Otherwise, as you mention, there should be an option that you can select stating that you cannot submit a proof of relationship since your host is not directly related to you.
As far as the Canadian Applying for Visitor Visa User Guide goes, a proof of relationship seems to be needed only in case you are visiting family members, spouses, grandchildren, etc. What you need to submit when visiting a friend is a letter of invitation from said friend. In this letter, the person must specify:
- complete name,
- date of birth,
- address and telephone number,
- your relationship to the person,
- the purpose of the trip,
- how long the person plans to stay in Canada,
- where the person will stay, and how he or she will pay for things, and
- when the person plans to leave Canada.
This is where you should explain your relationship with your host.