- "I want to be friends with [Mii]."
- — Mii, Tomodachi Life
When Miis become friends, they either talk to each other in their apartments, share their level-up gifts, or hang out at various locations. If a Mii develops feelings for another Mii of the opposite gender, they could confess to them and begin to date. If they fight, this could cause them to stop being friends if it fails to be resolved. If the player helps a Mii befriend another, that Mii will gain happiness.
Occasionally, a Mii will have a problem icon, with it being black in Collection and orange in Life. Upon entering the Mii's apartment, they may tell the player they want to become friends with another Mii and ask what they should do to get along with them. The player is given four options, with certain personalities associated with certain options.
After choosing, the player will speak with the target Mii and say that there is someone who wants to be friends with them. In Collection the target Mii will go to the other Mii's apartment, while in Life the Mii will go to the target.
The two will talk for a few seconds, and if they click (meaning the player chose the right options), they will wave and stars will appear around them. The Mii will be happy afterward, with the caption "It went great!". This is followed by the Mii saying, "It worked! We're friends now, thanks to you!" However, if they don't befriend each other, the stars won't appear, and the Mii will say "We're not quite friends yet..." afterward.
A rare occurrence in the game is that Miis can befriend each other without player request; the player can see the two Miis talking to each other outside either apartment.
Asked to Be Friends
In Life, there is a chance that instead a Mii will have a problem where they heard someone wants to be friends with them. They will ask the player whether they should go and if the player agrees then a short cutscene similar to before will play. However, in this one the Mii will answer the door for the asking Mii, who is invited in.
If they become friends, they wave as the stars appear and the "ding" plays, and the Mii will be happy afterward, saying "We're friends now!"; if they don't become friends, the Mii will say, "We didn't really click, so we didn't become friends this time." or "We're not friends yet...". The Mii who answers the door will do certain things according to their personality.
Introducing Two Friends
In Life, there is a chance that a Mii will want to introduce two of their friends to each other. If the player agrees, the Mii will ask what to talk about to help the Miis get along. After choosing one of the four options given, a cutscene will play where the first Mii will invite over their friends to their apartment.
The first Mii will introduce the two to each other and they will begin talking. The conversation will last a little longer than the cutscene between two Miis. During the conversation, the Miis will laugh, either one laughing or everyone looking surprised before bursting into laughter, the opposite Mii will be confused, or the introducing Mii will have to help them out. At rare times, the two Miis might talk at the same time.
Assuming all goes well, the two Miis will become friends with each other and the first Mii will thank the player.
If two friends spend time with each other long enough, they have the potential to eventually become best friends.
Best friends get along better than normal friends, and rarely ever fight. If the player plays long enough, most Miis will get a best friend. This state is achieved by two Miis being engaged in a good conversation (shown by happy faces and/or laughing). When this occurs, the same animation that plays when 2 Miis become friends will play, but accompanied with text saying, "[Mii 1] and [Mii 2] became best friends."
If two best friends have an argument that lasts for a while, a sting will play with the Miis having worried faces and a message will pop up saying "[Mii 1] and [Mii 2] became friends." The two Miis will no longer be best friends.
This relationship is not to be confused with the 100% friendship status on the Compatibility Tester.
- It is possible for two Miis to become best friends offscreen without the player watching. Goes the same for them losing their best friend status.
- It is possible that a Mii can dump their best friend by becoming best friends with another Mii. This will not cause any sadness, however.