Mc has a chat group and also a gamer system and is reborn into Skyrim. Chat group has Mobius from Honkai impact PE, Kiana (herrscher of finality and also clone) Honkai Impact current era, Stelle (HSR), someone from fate but hopefully it is Scathach, Gu Yuena (Douluo dalu/Soul Land), Brunhilde (Record of Ragnarok), and other worlds like Highschool dxd, Toriko, Foodwar, slice of life anime or romance, Toaru, etc. Gamer system is secretly the child of Akashic Records and is sentient and is female. The system includes everything like Evolution, bloodline, shop, inventory, gacha, quests, music, multiversal travel, and etc. MC is male and was very good at cooking and is talented at martial arts and weapons specifically sword, spear, and staff. MC was studying to become both a scientist and neurosurgeon. MC was born into a rich family but his parents had died and he only has a younger sister left and both of them are identical just different gender. When MC died the sister committed suicide and she got reincarnated into another world which is black clover (half elf and human and is the sister of the unborn child of Teita and Licht) and was kept safe in a magic spell made by Secre which eventually was undone into the canon and she's the same age as the main cast) or fairy tail (cousin /close relative of Zeref and Natsu with her magic being illusion dragon slayer magic taught by the Illusion Dragon Queen and Time God Slayer Magic and is the same age as Natsu being a year older) and eventually joins the chat group and the mc didn't know but thought that she was familiar and similar to his sister in personality and wouldn't find out the truth until later. The sister is also a year younger then the MC and loves her brother but never revealed it and is a bro-con since it was incest but now after her reincarnation, they aren't blood relatedanymore, if you don't like it then you can just make her the step sis of the mc instead btw. She is very strong mentally and good at fighting and intelligent. She is also a very good singer.
MC created a breathing style called the Omnigon Breathing in his past life which is in the fanfic that I recommended. MC sister also has breathing techniques called the erasure breathing style as well as chaos breathing style and void breathing style and illusion breathing style. She mainly uses the chaos breathing style however which is the second strongest that she has with erasure breathing style being the strongest and void breathing style the third strongest and illusion magic the weakest of her breathing styles.