Fate's final master

Zelretch's final moments

As the months and years go by, Izuku learns what he can with Zelretch, well more accurately Zelretch teaches Izuku the basics. Once he's done with the basics, such as getting through a barrier, he is put into a dangerous situation that increases his reaction time. For getting through the barrier, he was told that if he didn't get through within a certain time, at first it was an easy punishment such as none of his favourite things for a week.

But lets go over a brief summary for each year, shall we? Just know that he has been taught school stuff the entire time, I won't tell you how intelligent he has gotten.

Years 1-3: He mainly had fun, however did small exercise for his body along with reinforcement to make sure he gets used to activating his circuits for the future. 

Years 4-6: He slowly increased his exercise routine, along with adding a couple more spells into his list. Zelretch has also started teaching him good and proper with all the spells he knows.

Year 7: Zelretch has started sending Izuku into barriers that could wound him if he doesn't take it down promptly. This is also the year Izuku has started his stealth training for the future.

Year 8: He has been sent to another world, this time however he is facing off against enemies suitable for his experience. He managed to learn Emiya's tracing abilities before hand so he could trace weapons. Though he doesn't have Emiya's luck so he could trace more than just bladed weapons. However because he is still inexperienced in it, he primarily goes for the bladed weapons.

Year 9: He has managed to trace bows, medieval weapons and not that many guns. As his experience grows, he is thrown into fights with opponents around his skill level if not slightly higher. He has even branched into multiple magecraft branches during the times Zelretch has told him he can't use any weapon related magecraft, only spells.

Final year: Zelretch teaches Izuku how to summon heroic spirits, however none have been summoned yet. Izuku also manages to master the Emiya time magic, having mastered it to such a degree that he could expend some of his mana and get the same effect as someone with a quirk that affects time on a large scale, providing the quirk doesn't allow time travel.

(A/N: I know in the future of the MHA world, potentially time travel could be a quirk, but I refuse to allow Izuku do that unless absolutely necessary by using the Second Magic. Going to another world as a training trip with classes 1-A and 1-B, more likely)

However, Izuku and Zelretch are chatting in the latter's final moments, like how Shirou talked with Kiritsugu and started down the path to becoming his Archer self. Thankfully Zelretch has told Izuku that while heroes seem like they save everyone, they in fact can't save everyone, they are only human after all.

Izuku understands, and has responded with "With this knowledge, I'll save the ones that I can save. I will also save their smiles by sitting with them and hearing their problems." This gets Zelretch to smile, knowing his successor that he has dubbed the successor to the Second Magic, won't be foolish like a certain Emiya.

{Meanwhile, with that certain Emiya back in the 5th holy grail war}

"*ACHOO*" EMIYA (A) sneezes, getting Rin's attention. Rin asks "Actually Satan, why did you sneeze?" "Someone is talking about me. Not sure who it is though, also I'm not Actually Satan." he says, responding to Rin. 'Hmm, snarky attitude, reluctance to help unless needed, appears out of nowhere to give critiques more than anything. Nah, he's Actually Satan alright.' Rin thinks

{Back over to Izuku and Zelretch}

Both just calmly sit there, exactly the same as when Kiritsugu and Shirou had their 'Hero of Justice' chat.