Natsu No Arashi! (2009) S1E09

At the Ark Coffee Shop, the owner makes a special request to everyone. She asks them to travel back into time and bring back non-expired mackerel sushi so that she can eat it. Kaya strongly opposes to such a ridiculous request, while Jun states that if you have the ability to go back you can essentially do anything. This causes a huge debate on the ethics of time travel and changing history and if they were to jump back to an altered reality.