Anyone tried using Rubber Flexx? Do you think this tape and rubber paint will stop a leak? Interesting two part system. Thoughts?

Hello, We are having a problem with the existing eaves and downspout layout on our prow roof. The photo attached is an example of the design we have. The green areas show the existing eaves and downspouts which collect the majority of rain water from the roof. Our problem lies with the extended prow roof area in blue. There is no gutter along the blue edge. The rainwater which hits that portion of the roof falls directly below onto our deck. We stained our deck last year and you can already see a a line of damage where the stain has worn away in the exact shape of the roof line above. What’s the solution for these types of design? Would it make sense to hang a gutter on an an extreme angle (45?) to match the roof line and join it together with the horizontal green gutter? How else to deflect that rain water elsewhere? Thanks