I will start with names here and add locations, special terms and other relevant information as the novel translations advance.
Names
Baumeister family
Wendelin von Benno Baumeister – MC; 8th and youngest son; only magician in the family; Founder of a new branch family; appointed as Baron
Artur von Benno Baumeister – Father of MC, head of the household and the Baumeister territory.
Johanna von Benno Baumeister – Mother of MC.
Kurt von Benno Baumeister – Eldest son; successor of household. Dead
Hermann von Benno Baumeister – 2nd son; successor of the branch family. New successor of Knight Baumeister territory.
Paul von Benno Baumeister – 3rd son; removed from succession, a guard in the royal capital. Appointed as Associate Baron with a new territory.
Helmut von Benno Baumeister – 4th son; removed from succession, a guard in the royal capital.
Erich von Benno Baumeister – 5th son; removed from succession, successor of the Brandt household.
Leila – Mistress of Artur
Walter – 6th son and born to Mistress Leila, thus outside of succession.
Karl – 7th son and born to Mistress Leila, thus outside of succession.
Agnes – Eldest daughter, born to Mistress Leila.
Karina – 2nd daughter, born to Mistress Leila.
Amalie von Meinbach – Kurt's wife.
Marlene – Hermann's wife.
Leon – Hermann's eldest son.
Klara – Hermann's eldest daughter.
MC's Teachers/Patrons
Alfred Reinford – MC's first magic teacher, a Talking Corpse; purified by MC as his final exam.
Amadeus Freitag von Breithilde – Margrave of Breithilde; employer of Burkhart. Patron of MC.
Burkhart Ringstadt – Alfred's teacher and MC's second teacher; employed by Margrave Breithilde as Head Magician.
MC's Adventurer Party
Ina Susanne Hildebrandt – Vassal of MC. Member of MC's party since his Adventurer Prep School days. Proficient in spear wielding. Her family members are loyal retainers of Margraviate Breithilde. Childhood friend of Luise. Betrothed to MC at the age of 13. Pregnant with his child as of Volume 13
Luise Jorlande Orphelia Orwin – Vassal of MC. Member of MC's party since his Adventurer Prep School days. Uses a magic combat style, trained under Armstrong in the capital. Betrothed to MC at the age of 13. Pregnant with his child as of Volume 13
Erwin von Arnim – Vassal of MC. Member of MC's party since his Adventurer Prep School days. Skilled in sword arts. First friend MC made.
Elise Katharina von Hohenheim – Granddaughter of Cardinal Hohenheim, proficient in Holy magic, especially Healing. Betrothed to MC at the age of 12 (same as MC). Pregnant with his child as of Volume 13
Wilma Etol von Asgahan – Has Hero syndrome. Always hungry. Affiliated with Minister Edgar. 13 years old at the time of joining MC's party. Betrothed to him at the age of 11.
Katharina von Waigel – A typical tsundere character, joins Wendelin's harem during the Demon Forest arc. Strives to recover the Waigel's household's reputation. Her nickname as adventurer is Storm. Betrothed to MC. Pregnant with his child as of Volume 13
Katia Eulenberg – Boyish girl. Brown twintail hairstyle. Famous adventurer and daughter of a backwater noble. Married MC at an age of 20.
MC's household members
Roderich – Illegitimate son of Head of Financial Auditing Rückner and manager of the royal capital's mansion
Monique – Maid at the capital's mansion. Childhood friend of Elise, daughter of a maid in the Hohenheim household.
Brandt family
Rüdiger Wilhelm von Brandt – Current head of the Brandt family.
Marion Wilhelm von Brandt – Rüdiger's Wife.
Miriam Wilhelm von Brandt – Only daughter of the Brandt family and Erich's bride/waifu.
Important Persons in the Kingdom
King Helmut – 37th King of Helmut kingdom.
Finance Minister Rückner – retainer under the Helmut Kingdom; noble ranking is marquis.
Minister of Agricultural Affairs Brückner – retainer under the Helmut Kingdom.
Minister of Military and Naval Affairs Edgar – retainer under the Helmut Kingdom.
Royal Head Magician Klimt Christoph von Armstrong – retainer under the Helmut Kingdom; friend and rival of Alfred; One man army.
Cardinal Hohenheim – High-ranking clergyman of a major faith in the Helmut Kingdom.
Sir Warren – Company Commander of the Chivalric Order of Helmut Kingdom's Royal Guards.
Head of Financial Auditing Rückner – Younger brother of Finance Minister Rückner. On bad terms with him.
Side Characters
Kunz Flieger – Captain of the magic airship in Chapter 26.
Leopold Bergim – First mate of the magic airship in Chapter 26.
Viscount Mongérard – Intermediate-ranked noble with close ties to the Brandt family; former groom candidate for Miriam.
Klaus – Village chief of the first village in Baumeister Knight peerage territory, his daughter is the Mistress of MC's father.
Jürgen – Village chief of the second village in Baumeister Knight peerage territory.
Fritz – A random villager, appeared in Interlude 8.
Sebastian – Formerly Cardinal Hohenheim's butler, now appointed to Elise.
Abel – Butler of the Baumeister main household.
Artur – Merchant; former (adventurer) party member of Burkhart.
Lobus – Butler of the Main Baumeister household.
Helenna – Servant at the Main Baumeister household's mansion.
Locations
Lingaia – The continent's name.
Helmut kingdom – The kingdom the Baumeister territory belongs to.
Urquhart Holy Empire – The neighboring empire north of the kingdom.
Breithilde – The margraviate close to the Baumeister knight territory in the southern part of the Helmut kingdom.
Holmer – The margraviate at the western border of the kingdom.
Browig – The margraviate at the eastern border of the kingdom.
Stadtburg – Royal capital of Helmut kingdom.
Barude – Imperial capital of Urquhart Holy Empire.
Breitburg – Seat of the Margrave Breithilde and biggest city in the south of Helmut kingdom.
Demon Forest – The monster domain adjacent to the Baumeister territory.
Savage Lands – The uninhibited lands south of the Baumeister territory where MC explored, hunted, etc. in his childhood.
Palkenia Grasslands – Liberated monster domain. Grain-producing area close to the capital of Helmut Kingdom's capital Stadtburg.
Money Conversion
One copper coin is one cent
Ten copper coins or one copper plate are ten cents
Ten copper plate or one silver coin are hundred cents
Ten silver coins or one silver plate are thousand cents
Ten silver plates or one gold coin are ten thousand cents
Ten gold coins or one gold plate are hundred thousand cents
Ten gold plates or one platinum coin are one million cents
Ten platinum coins or one platinum plate are ten million cents
Miscellaneous
Magic Core – Harvested from monsters.
Magic Gem – Processed magic cores.
Ancient Magic Civilization – A culture having lived on Lingaia a long time ago. They have left behind ruins which conceal Overtechnology such as the magic airships. They were far more advanced than the current nations and thus the resources drawn from their ruins are highly evaluated.