Responses
At least 10 years probably.
WHAT
Although Shizuku started young as a bodyguard, it appears that he was assigned to Ichika well into his career and he looked at least in his late teens at the time, while Ichika looked like a grade schooler.
This is all my speculation though.
No, not that large. Ichika most likely 18 ish. Shizuku probably around his mid 20 at the most.
And what is exactly the age gap between them?