As some others have pointed out, I don't really see a love triangle happening yet. Though the introduction of the character is pretty ham-fisted, best case scenario for the plot now with the childhood friend introduced is that Rika gets over the love rival aspect in the first 2 pages of the next chapter, Takuya and Rika go back to Tokyo and the childhood friend never appears again, but the main romance is back on track. That's the best scenario I can see for now but we all know that's not happening soooooo