The ending of the Haikyu manga sees the main characters having accomplished their goals and leaving a lasting impact on the volleyball world. It wraps up their stories in a satisfying way.
I'm not sure specifically what the 'giant little brother story' is about as it could be any number of things. It might be a story where a little brother has some sort of extraordinary growth or ability that makes him 'giant' in a metaphorical or literal sense.
I'm not sure specifically as there could be many different stories with this title. It might be about a little girl who has some sort of giant - like qualities, perhaps she is very strong or has a large presence in some way.
A little girl lived on the edge of a magical land. One day, a giant appeared. At first, the girl was terrified. But she noticed the giant seemed sad. She mustered up her courage and approached him. The giant told her he was lost. The little girl, using her knowledge of the land, helped the giant find his way home. In return, the giant promised to protect her village forever. And from that day on, they were friends and the little girl had a very special and big protector.
I'm not sure specifically which 'little giant girl story' you mean. It could be about a girl who is small in stature but has great courage or extraordinary abilities, like she might overcome big challenges in her life, perhaps facing difficulties in a small town but still achieving great things.