This bonus is directly taken from the main series. I read the entire Shura no Mon third arc after I finished translating volume SnT 4 (It's okay, you're not missing anything much. What happened was Tsukumo beat up some boxers, angering every American he can find, had a fight with Jilco, become world champion, and Maiko is still not getting the D. But she did confess to Tsukumo and is officially his girlfriend).
And I must say, this epilogue scene almost made me cry like Azuma. Try to do the same! But if you do cry, I understand....