[X] Lie about what you saw. You won't tell anyone what you really saw, but you need to say something.
-[X] You were attacked by your childhood protector who tried to kill you before you entered the Academy, and this time he was going to finish the job.
We can't both be truthful to our team, and keep the Gamer-thing a secret. Telling the truth here in the spirit of "We must have no secrets. We must know each other as closely as we know ourselves" but hiding our Gamer-thing would just be hypocritical and a lie in itself. If we don't want to reveal the Gamer-thing, we have to choose untruthfulness.
I don't want to choose silence, since I actually think that Kurenai is within her rights to demand the truth from us, unless it's protected be law like a Clan Secret.
Thus, we choose the best kind of a lie, one that has many elements of truth in it. It is a lie, because this is not the thing that Daisuke feared the most, but close enough that it should fly.