Nisekoi

Raku Ichijou is your Ordinary High School Student. Well, as ordinary as he can be, being heir of a Yakuza family, a position he's not too happy about. Still, he lives a mostly carefree life until one day he crashes into (or, more precisely, is crashed into by) Chitoge Kirisaki - his class's new transfer student. This causes him to lose his most precious possession- a pendant given to him by his first love ten years earlier. Some harsh words are thrown and even though Chitoge eventually helps him find the pendant, the two of them are off to a bad start.

If that wasn't enough, a new gang shows up in town and start getting into fights with Raku's family - a conflict that could escalate into full-blown gang war. Through the power of coincidence, the gang's leader turns out to be not only Raku's father's old friend, but also Chitoge's dad! Together the two heads devise a plan to calm down their rowdy subordinates: Raku and Chitoge will have to pretend to be a couple! The two of them are not too happy about that, but agree to play along to avoid a bloody conflict.

Thus starts a story of love, lies, twists and promises. How long will Raku and Chitoge manage to fake their feelings? And how long will those feelings stay fake?

Tropes used in Nisekoi include:

All According to Plan: Marika uses this so often that Raku invokes it word-for-word after she'd kidnapped him to a tropical resort and then their small boat sank:

Raku: And I'll ask just to be sure, but ... "This was all according to plan" isn't going to be the next thing out of your mouth, right?
Marika (smiling): My, Raku-sama. What kind of idiot would plan for us to be stranded together on an uninhabited island? Kya♥
Raku: I asked you because I had a feeling that an idiot was standing right in front of me. You kidnapper.

Bromantic Foil: Shuu Maiko, Raku's best friend. Half the time he meddles to help Raku. Other half- because he thinks it's funny.
Bifauxnen: Tsugumi.
Breaking the Fourth Wall: Done occasionally; for instance, in Chapter 112, a policeman last seen some five volumes before asks to speak with Marika:

Marika (looking over her shoulder at the readers, while waving towards the policeman): To the nearly 100% of the readers who have forgotten this person...I shall explain who this person is.

Cat Smile: Practically Shuu's default expression.
Censor Steam: Used repeatedly in Chapter 23.
Childhood Marriage Promise: One of the most important plot points is that Raku made one with a girl he knew ten years before the start of the series. Unfortunately he doesn't remember her name or face. His only lead is that she has the key to the lock in his pendant.
- It's revealed early on that Kosaki Onodera has a key from a childhood promise she made but seems unsure about.
- Later we find that Chitoge also made a promise with a boy whom she can't recall. In fact it's strongly implied that they made the promise with each other.
  - As of Chapter 27, Onodera claims to be the promised girl, when asked by Raku.
Class Is in Room X-01: Despite how generic many of this series' other elements are, it averts this. The class the main cast is in is 1-C.
Clueless Chick Magnet: Raku. He even recognizes that the "symptoms" Tsugumi lists suggest she's in love -- but he doesn't catch on that he's the one causing her to react that way. This is just five chapters, and less than two weeks, after her arrival.
Defrosting Ice Queen: From the start, Ruri has despised Shuu. Then in Chapter 128 she admits to herself that she feels "like something is getting caught in my chest" when he leaves her name out of the long list of girls he "loves."
Exploding Closet: Chitoge's.
Fan Service: Kept at very low level considering the genre... until the 2 part Hot Springs Chapter that is.
First-Name Basis: Chitoge decides that she and Raku should call each other by their first names after he saves her in the forest.
Genre Savvy: Shuu Maiko and Ruri Miyamoto
Gratuitous Polish: The childhood promise Raku and Chitoge recalls includes a Polish word -- "Zawsze," meaning "forever," "eternally," "always," something like that -- despite none of the characters being identified as Polish.
Hidden Depths: Ruri has a very emotional moment when she tearfully tells her great-grandfather of all the friends she's developed -- Kosaki, Chitoge, Seishirou, Marika (sort of), Raku ... she even includes Shuu, "I guess." Listening outside the door, Shuu shows an uncharacteristically gentle smile....
Lonely Rich Kid
Real Men Cook: Raku is an excellent cook -- having to take care of his Yakuza family turned out to be a good training.
- The girls, on the other hand, or anyway Kosaki and Chitoge, are lethal chefs.
Memento MacGuffin: The pendant Raku carries is not only a memento of his first love but also the only clue he has of her identity.
- Onodera and Chitoge also carry around a key as a memento of a promise ten years ago. Sounds awfully familiar...
New Transfer Student: Chitoge transfers into Raku's class in chapter 1. She's transferred schools a lot before because of her dad's travels.
- Later Seishiro Tsugumi
  - And still later, Marika Tachibana
  - And Paula McCoy
Not So Different: At first Chitoge and Raku seem to be polar opposites, but eventually they find out that they have surpassingly similar experiences as heirs of crime syndicates.
Shipper on Deck: Dear gods, there are so many. Ruri in particular physically shoves Kosaki together with Raku ("Oh centrifugal force! Can't help it!"), and has more than once told Kosaki to "rape" him. Claude is about the only member of the criminal gangs who doesn't support Raku-Chitoge. He's shown a number of signs implying Bodyguard Crush....
- And then there's Kosaki's little sister Haru, who supports Kosaki-Raku despite having a crush on Raku herself, and her friend Fuu who's pushing Haru-Raku although she may herself have feelings of (or beyond) Romantic Two-Girl Friendship for Haru. And Tsugumi's friend Paula is a Tsugumi-Raku shipper....
Troperiffic: Think of a Romantic Comedy trope. There's good chance that it applies.
Tsundere: Ruri has a bit of this, but only toward Shuu. On one occasion, after he'd loudly admired the other girls' appearance but was more casual about hers, she hit him with what the narrative text called an "I-don't-really-care-but-I'm-still-kind-of-pissed-off-punch."
Twice Shy: Raku and Kosaki.
Unprovoked Pervert Payback: Averted. Raku walks in on Chitoge in the hot spring, but she quickly figures that it's because Claude switched the signs to destroy Raku's reputation.
- Played straight whenever Tsugumi is involved.
Wham Chapter:Chapter 13 in which Chitoge remembers that she once made a promise with a boy. A promise that is word for word identical with the one Raku made.
Yakuza
Zettai Ryouiki: Chitoge sports impressive Rank A one.