She may be putting on a lower voice, or she may just not have a distinct voice. A lot of people sound similar if you're not actively trying to differentiate between the voices/identify a voice.
I had 2 questions reading this chapter.
1. How much did they spend??? On top of the ticket prices, food is hella expensive at theme parks right?? And it seems like Kurumi has done this before considering she seemed like she knew what she was getting into???
2. Rentaro doesnt have the same...
In terms of personalities of the characters, I also felt that they were rather stagnant and I wasn't as interested in their story as I was for the other one. I persisted as it was the same author. Still a pity though, it sucks whenever a series gets axed.
Yeah, it's rather fucked up to be pretending to be him in front of his sister, when he's already dead. Oof. That's also nightmare fuel when she finds out.