CallmeMISTER
It's not as bad as I thought last chapter (since you had the mc lie about something that would've ruined the story), but I'm still uneasy. Time travel can ruin stories very easily and is usually done best when it's either done very sparingly or all the time (and is the premise of the story, e.g. Doctor Who, Re: Zero), and even then it usually isn't very good. I'm also not really a fan of his every move being manipulated and dictated by someone else, even if that someone else is his future self. It makes the story lose tension and every decision he makes seem worthless. It's fine if it's revealed he was being manipulated all this time as a plot twist (like what you revealed here), but I'm not okay with that continuing forwards with our knowledge of it.
I don't know this spear is supposed to be as strong as a longinus is a good one. It would be interesting if she could get stronger with time. Drandal type becoming Ex-Durandal. After all, longinus are extremely powerful for a reason, so allowing room for the weapon to grow in power would make a lot of sense. About Grall I see many authors rescuing Valerie in the beginning. As the story is not following the original version, it may be that future plot holes can be avoided. Overall the story is very good. The giant reminded me of Susanoo.