Bayern is becoming your black beast, whenever you face the Bavarians in Champions it doesn't end well for you but you've done a magnificent Champions League run this season regardless of this result and with a lil' tweak or two this squad could easily become serious Champions League contender material for the next season.
About the domestic competitions, excellent league run (champions and with a league score record to boot) but shame on the cups though (specially the cups, losing a final hurts.... losing against Chelsea hurts even more ¬¬), if you keep up such a good work you'll end up establish a Saints' supremacy for quite a long while.
And last but not least... About Asensio, if I were you I would let the lad go. Yes, he's a fantastic player and of course the team level would plummet with his leave but he has shown a remarkable lack of commitment and that's even worse for the club than his departure (maybe it's just me but I wouldn't keep a player that won't give his all on the pitch around) you can take quite a hefty sum for a player of his caliber and use it to strenghten the squad (you could cover more than one area with the money given for him).
Anyway, it was a good season but I'm sure next will be way better so keep the good work up ^^