There is nothing sadder than a side love." NAME_1 said with a slight smile on his lips. What are you talking about? NAME_2 tried her best to suppress her agitation and asked back.
It's about NAME_3. NAME_2's heart thumped loudly. NAME_1 watched NAME_2's reaction as if he was enjoying it.
What? NAME_4 is my little brother." NAME_2 answered calmly.
But we're not blood related, are we?
'Yes, but we are .......'
NAME_4 doesn't think of you as his sister.
How do you know?
The voice became unintentionally loud.   On the contrary, he looked increasingly happy. He said, "If you had seen the way NAME_3 looks at you, you would know. He always looks at you as if you were a goddess he worships. You're not so young that you don't know what that means.
It's ......." Eyes had nothing to say. The actuality is, it's not just a matter of the time. 
And she couldn't suppress the fact that she felt happy about it.
But on the other hand, she also knew that this feeling was unforgivable. NAME_4 was still in the eighth grade. And she was twenty-one years old. I knew that it was not an acceptable relationship. Besides, NAME_4 had friends and club activities. He had to have a normal partner.
This is a continuation of the previous sentence. Summarize this sentence.