The "something" is referred to love. Only, person who can see it are the whole bunch of people wanted to have it. because that's the way its meant to be. its what said at start and end of the super duper series. However, somehow it links to the conversation ryuji had with kushieda , about the ghost and UFOs on the beach house.As, Kushieda wanted to see how ghost looks like. It might be referred to the love we have for those who surround us. as in case of Taiga and Ryuji, the whole time the thought themselves as friends and never realised that was the love which don't let them move away from each other.And at last only they were able to see it as they both craved for it for their life. Both of them missed the love from their family. and found each other.
the ending was very satisfying and letting me down too. As Kushieda and Ami chan, both developed the feeling of love and affection to Ryuji. While kushieda thought taiga needed him more and she was feeling guilty of being trying to steal Ryuji from her if she confesses her love towards ryuji while, Ami was the most mature girl in the school , who believed that Ryuji and Taiga both love each other. And she can't have Ryuji because trying will only give her pain just like Kushieda.
The biggest sacrifice was made by Kushieda, she was betrayed by both his love and Best friend. While, I felt super bad for Ami too as she was badmouthing like taiga but she is always helpful to both Ryuji and Taiga. Honestly, Kushieda able to confess her feelings to both ryuji and Taiga in end episode - Confession. But Ami never able too, she only kept it to herself. And that was very painful.
Don't wait for Season 2, as the story was never meant for next season. Its complete on its own.Also, don't forget to watch the real ending after the finishing song in the series.