Vol 3: Ch 112 - Other Identity Revealed
The two didn't run in order for them – the passerby – to not let their attention got more caught from them.
Getting caught red-handed by them was already troublesome since this time they got strong evidence for them that they're kissing and hugging, so for not getting more attention from them, they walk like nothing happened though they already have been caught by them. Though they won't deny if it got exposed and will remain hidden at the moment when it's not exposed but still it will be going to be a mess if someone exposed it.
Rei and Tae walk to where they park the car but before entering, they make sure that no one and nobody following them but alas they really got a follower who followed them and now the two are hiding behind the car and just listening to their conversation.