Based shounen picked up his waifu and took her away.
Also someone already pointed it out, but the kid was upset at how the situation in the bar made the gulf between them so obvious.
So he got upset and just abducted her. Pretty cool if you ask me.
His mom works at standard Japanese shady bar involving alcohol and prostitution, so she should be OK with such things. Especially when her son is with good looking office lady and not some yakuza bastards or something like that. She might be really happy with his choice!