"It feels like I get this surge of energy."
Nah, summer makes me tired. Harder to sleep, and if it's hot that drains energy.
Even if you have similar tastes, picking the exact same book at the exact same time isn't "bound to happen".
"I wonder if I showed another weird side to him..."
If he said he liked it, it's nothing but positive.
That looks like one of those food delivery backpacks.
Yuika should just "accidentally" walk in on those two, and ask if they're shopping together.
The left one looks more like a dress than a swimsuit. Both look good, though.
If you ask if it suits you, he will naturally look down either way. Can't judge it by looking you in the eyes.
"I see, you got fat, huh?"
If that's not a line you'd like him say to you, don't say it to him. Most girls would clobber a guy saying that to them.
I don't know what it looks like over there, but most of the time, if I get lost somewhere, I just head towards some place where I know I'll run into something I recognise.