This is book number 7 in the Rascal Does Not Dream (light novel) series.
UNDOING WHAT CAN’T BE UNDONE.
Sakuta had been ready to give up his life, but nothing could have prepared him to keep living like this. Now he must find a way to carry on even when it feels like tomorrow will never come. And even if it does, why should he care when the love of his life is already gone? Of course, he can always count on Shouko to show him the way forward in his darkest hour, just like she did all those years ago. As he gathers the strength and courage Mai gave him, Sakuta readies himself to do whatever it takes to rewrite the past.