I Have Made A Reservation

Sunny Yamamoto was stunned upon hearing the question as he clearly had no idea what the connection was between the two. 

However, he soon realized something, and with the shameful tone, he said, "It's true that my grandmother had passed away three weeks ago, but it has nothing to do with Reina, it was all about me."

From what Kimura Kazuki heard from Sunny Yamamoto since he lived with his grandmother, he and Rieko were being caught red-handed once in the house by his grandmother. Therefore, he could only lie to his grandmother and claimed that Rieko was his girlfriend.

However, his grandmother soon found out about the fact that Rieko was with other men, she had not stopped nagging him ever since. Even though he replied to her apathetically, his grandma would still keep going until he had finally expressed his trust for Rieko. Only then, his grandmother would eventually stay out of his business.