
Originally Posted by
alfheimwanderer
There are a number of pre-requisites involved, which involve piquing Sion's curiosity, proving useful to her, and continuing to prioritize and protect her interests. In the past few years, Shinji has not been doing badly in that regard, as he has helped her to obtain a skilled Vice-Director, qualified for the Potions Competition, and has not disclosed his involvement with her to Zouken - or to anyone else who doesn't already know.
What I will say is that he does need to continue to grow in his abilities so he will not be a liability, as Sum of All Fears will be the culmination of all the plot threads to date, including both the Holy Grail War and the subject of Sion's personal quest...