You are missing the "de". The expression would be "LA CONCHA DE LA LORAAAAAA".
To the others who are reading this. Yes, they're cussing. But it's not really an insult that you say to someone, but something you say to express that something makes you mad. Kinda like a "FUUUUUUUUCCCK" being diferent to a "FUCK YOUUUUU" I guess.
This is sweet and all but aren't we all forgetting that in the last chapter, Tateyama, the girl Shiotani went to University with, said she's done "putting it off"? This isn't the end just yet fellas. Prepare for some drama.