Sayonara Isekai, Mata Kite Ashita

The world he woke up in is long dead, dusted in ashen powder, and yet Keisuke still sees splashes of color as he travels through it. For the longest time, he's wandered alone across the deserted landscape, clinging to the hope that something—or someone—might be out there in the emptiness. When he finally stumbles across that someone, even more threads of color start to seep into the ashen world around them. This time, when Keisuke sets off down the road, someone sits beside him in the passenger seat. The first acquaintance he's ever made here, his first companion in this barren world. They're both traveling in search of something, and after searching alone for so long, maybe they'll have better luck working together? Their only lead is a witch who can answer any question—for a price. What will the two ask her, and what will she be able to tell them? More importantly, what will it cost them, and will they be willing to pay the price? (Source: J-Novel Club)