With the second part of the 2.1 update, the character of Sangonomiya Kokomi arrives and she is a character who will have a very specific role since she is care-oriented . She will therefore act as a healer for your team. You should know that Kokomi is a healer who can heal your other characters via his elementary skill but also thanks to his burst. The latter allows her to benefit, like Barbara's E (elemental skill), from a buff that allows her to heal her teammates when she hits an enemy with a normal attack but also to increase the damage of the ghost jellyfish that she summons with her elemental skill.
The healing provided by Kokomi is based on her max HP, so you will have to focus on this stat to best heal your allies. This stat is also useful for increasing the damage she does once her elemental unleash is activated. His second passive gives him a damage bonus based on his extra healing bonus so you have to rely on this stat as well, although max HP is still the main stat.
You should also pay attention to the Tempered state (as for Barbara) which is applied to Kokomi from the use of Transcendence: Doom Omen, which can therefore allow you to be frozen if you face Cryo enemies .
In case you hope to see Kokomi as your DPS, you will have to wait for another character because even if she can be played with the 4-piece Soul of the Castaway set, she will have a significant handicap conferred by her fourth passive which grants her a 25% healing bonus but which reduces his crit rate by 100%. She will therefore be able to do damage but she will not be able to take advantage of the bonuses offered during a critical attack.
To come back to Kokomi in general, this one is a healer who can be useful to you but which is absolutely not obligatory if you already have Barbara, Bennett, Jean, Sayu or Diona.
Recommended weapons
Artifacts
Of course, these characters are only examples and do not constitute all of the playable characters with Yanfei but just a small representation of what you can do. Your imagination will allow you to create your own teams and test according to your preferences.