Watchdog.

Terada Ayano, better known as Otose, is Gintoki's "landlord", or rather the old lady who lets Gintoki and company shack up at the top of her snack shop. She's best recognized as that creepy baba who demands rent from Gintoki every hundred episodes (or whenever he pisses her off) and occasionally complains about the Yorozuya's incessant screaming and trouble-making. Otose is often referred to by our silver samurai as that shitty old woman, if that clues you in on the way in which Gintoki shows respect for his elders. For the most part the relationship between landlord and tennant is comical at best, but it's pretty clear that Gintoki isn't the kind of guy you keep around because he keeps up with his rent or because he's cleans up around the place or anything. So why exactly doesn't Otose throw him out on his ass?

Most Gintama fans would reply that Gintoki and Otose shared a poignant, deep, beautiful moment in their tragic pasts, thus leading their fates to become intertwined. I on the other hand think that it's probably some sketch relationship and Otose is actually something of a cougar. However, when I tried to google search some proof, Google glared at me in disgust and suggested me a different result entirely. HDU GOOGLE. So I guess the jury's out on that idea for now. But real friends don't bone their best friends' sisters, fandom, remember that.

Otose first meets Gintoki one cold winter's day while she's visiting her deceased husband's grave. As she's about to set down her offerings of manju, she hears the voice of a cold and tired soldier from behind the headstone. He tells her that he feels like he's about to die of starvation and asks if he can eat the manju. Otose tells the young soldier to ask her husband first, but Gintoki devours them without even saying a word. When the old woman asks him what her husband said, Gintoki, ever the smart ass, replies with "Why would a dead person talk?" However, the battered samurai tells her that he made a promise with her husband as thanks for the food.

I won't forget this favor. This old lady probably doesn't have much time left. From now on, I'll protect her for you.
--Sakata Gintoki, Chapter 4
These words are very illustrative of their relationship, as it's a promise Gintoki never intends to break. While Otose certainly doesn't forget to demand the rent from the brokeass samurai, she's a character who's also well known for her big heart. Otose calls it a flaw of hers, but the fact of the matter is that she can't help but offer a hand to someone in need. Be it Gintoki, the (literal) cat burglar and her partner in crime, Catherine, or all the drunken idiots who come visit her snack shop at night for company and advice, Otose and Gintoki share the same desire to extend their hand to anyone who's in trouble. Moreso than his promise to protect her, it's likely that Otose sees and admires these traits in Gintoki and his work with the Yorozuya. Regardless of their differences, the two share the same kind of soul--it's no wonder that Otose couldn't possibly kick Gintoki out. (Plus, forilla, what 60+ year old woman would kick the most eligible bachelor of Kabukicho out of her house?)

Ever the samurai, Gintoki also faithfully upholds his promise to protect Otose. When an old admirer of Otose, Doromizu Jirochou, comes strolling back into Kabukicho looking for trouble, Gintoki is the first person to be on his guard. Once a close friend of Otose and her husband, Tatsugorou, Jirochou stations himself in the Kabuki District to be near Otose and protect the District that his friend Tatsugorou once did. Jirochou cares so deeply for Otose that he leaves behind his wife and child in order to be closer to her, but when shit goes down in Kabukicho and his daughter comes to town to stir things up, Jirochou's idea of saving Otose is to "kill her" and spare her from the chaos that's about to come. Gintoki of course, refuses to let any of this happen. He races to Otose's rescue and attacks Jirochou with all the ferocity of his days as Shiroyasha. It's one of the angriest states which Gintama readers/watchers have seen Gintoki in to date, and justifiably so. Gintoki is a character who upholds his promises and would put his life on the line if it meant saving Otose--his care for Otose and his friends becomes extremely evident in this arc--he's almost willing to disband the Yorozuya in order to keep everyone from getting involved in the harm he's willing to go through to protect Otose and Kabukicho.

However, despite their differences these men share a relationship with Otose that parallel one another more than they may realize, as Jirochou's daughter Pirako, points out:

Sure, you're both beasts tied down by your chains. But there's one major difference. One cares for this city and protects Otose in Tatsugorou's place. And the other... could really care less about the city, but loves the person who resides within it... so he protects both with all of his strength.
--Doromizu Pirako, Chapter 302
Otose is yet another character in Gintoki's life which he most likely feels indebted to--not unlike his beloved Shouyou-sensei, she extended a hand to him when he was alone, gave him a place to stay and allowed him to meet new friends. No matter how one may see their relationship: mother and son, old lady and caretaker, master and watchdog or just a simple landlord and tennant, Gintoki has made it clear that he and everyone at the Otose Snack Shop are part of his family, and no turf wars nor overdue rent can change that.