The novel can be said to break into three major arcs. The beautician arc, the Trade route arc, and the power up MMO and final boss Arc. I won't spoil the good drama snippets but the MC will embark on the "The Great Trade Routes" and meet new companions. A guy with lots of swords, a female thief with a natural flare for navigation, and a cook that fights only with his legs, fruits that give special abilities... sounds familiar? It literally steals cliches and elements from popular anime and games. Softporn as well...using his water techniques to knockout girls during fourplay... cough

it's a decent mediocre ending. Read further if you want to spoil

Well finally got around to finishing it. It seemed like the author rushed the ending. He introduced a lot of girls but they disappeared just as fast or was forgotten about. The MC creates a flying fortress powered by hundreds of female water disciples for the final confrontation. Everyone in his party including his mother become crazy overpowered. The MC defeats the final boss who is his half brother. His brainwashed father is reunited with his mom and the MC enjoys longevity with his harem.

The reason the protag started water therapy (in this case you people refer it to beautician) is because the norm for that service cost is very high and is in high demand due to its rejuvenating properties when compared to the holy system healing magic and its rarity (holy system users are more rare than water system).

The protag's mother is not as skilled as you all think, her water system is mainly based on physical type system and less on magical type (almost non-existent), that is also the reason why she is unable to use water therapy to rejuvenate herself and the protag does it to her instead, another reason is I assumed she isn't even talented enough to be enrolled into the magic school from reading the first few chapters when the protag is going thru the examination, hence another reason why she only taught the protag in the "feeling" and control of water system only.

The teacher taught the water system class magic-type only a few basic spells when protag just enrolled, water ball and water therapy (teacher also explains and pros and cons of water system magic-type water therapy vs holy system magic-type holy light healing) and also explains why water therapy is "high demand".

Since mother sold the house (can't remember how much she sold it for) they lived in to pay for protag's school fees and bought a smaller house nearer to school, the protag decide to test the theory if what the teacher said is true in regards to water therapy, so his mother could stop washing (iirc about 100 articles of clothing = 1 gold coin, school fees 1000 gold coins) clothes with ice freezing temperature water with her hands daily, due to it she is starting to show signs of suffering from fatigue and combined with a frail constitution to begin with (her water system physical-type is less than average, probably enough to fend off the occasional weak monsters level type encounters on the road if ever... or not).

Turns out the theory of what his teacher said about water therapy is true, so the money issue and mother is going to die if she keeps continuing her laundry job issue they are facing is solved with the bonus of instead of spamming water gun to increase his magic capacity (needed to cast spells or mana/MP) and increasing his affinity with water system element particles (needed in order to learn and cast higher level spells) he uses water therapy instead (one of the very few basic water system magic-type they were taught by the teacher).

Here comes a new issue, the 36 fire-wind system Main: physical-type users, because of the rarity (because able to use more than 1 element system is rare, and even rarer is having elements able to compliment each other) and powerful combination of fire and wind system, they are monopolize by the country, going as far to have their family as hostages/getting killed if they ever tried to run or escape from the enrolling into the school.

Also due to their fire-wind system, since magic is indiscriminate, their own magic harm themselves as well (even our protag suffers from this when he uses ice armor, classifies as advanced water: ice system physical-type so he does not use it much at all), so they suffer heat waves from their own fire magic and suffer dehydration of the skin from both heat and high speed moving via wind system during their training, which cracks the skin and exposing flesh, blood and veins.

Seasoned veterans of this fire-wind system do not wear clothing anymore as it causes more harm and pain due to the skin, blood and flesh sticking onto them when later removing those clothing (literally peeled off, so its very painful), so the country specially issued them a "cape" to cover their body with but to the view of public eyes (iirc the real reason are kept and its not known to the public) those "capes" are a type of representation of the prestigious, deadly and powerful fire-wind system users, also the more ugly one is, the more powerful they are as told from history (when the country deploys them to battle, a General's POV-wise iirc or author's, can't remember) also most of them does not have a second life to live from other and only able to live as living weapons (would you marry a 26 year old girl who looks like she is a 60 year old?).

So to the 36 fire-wind system girls, the protag is like a godsend to them, the only person in the country who is not a personal water system type for hire (teacher explains that all water therapy casters only cater to famous/rich social circles and is also very expensive), this water therapy rejuvenates and rehydrate their body and increases natural body regeneration speed, this way it will restore their appearance and to them its a second life they dreamed to have, able to get boyfriend, getting married, not looking like a 60 year old when you are only at the age of 26 etc, but will never be able to achieve that dream if they can't afford a water system user to cast water therapy on them and is also one of the many reasons they decided to serve him but it is not shown until later.

Also from this point on in-regards to the 36 fire-wind type girls who serves the protag, it gets dark from now on, the 36 fire-wind type girls CAN ONLY serve the country, the country literally owns them, they are treated as nothing more than living weapons, so if you want to find out you'll just have to read the novel.

The reason why the protag keep most (most and not all) of the money that the 36 fire-wind type girls earns for him by doing jobs he assigns to them is because he uses it to buy magical equipments and artifacts for them and himself, also used to expand his business (almost all the ideas are suggested by the "Big sister" who is the head maid, basically she is the brains of the protag's money making expanding business and she handles everything financial-wise), but he also said as long any of the 36 fire-wind type girls have a valid reason for wanting to withdraw more is alright, however most of you people forgot is that what the protag meant is the physical money on hand, the written money in the recorded bank books and contract is 50% of the profits that 36 fire-wind type girls brings in from jobs he assigns goes to them and forever to them and another reasoning is that they will be continuously running jobs for the protag while training, fighting off monsters and bandits along the trade route so it kills 2-birds with 1 stone (so it is assumed they won't have time to go shopping nor sight-see however he gave them more than enough to buy daily necessities as well), its also the reason why the protag assign those trade jobs to them and from this point on the protag has already stopped spamming water therapy to improve his magic capacity and water affinity so he solved the money issue this way instead.

Later on you will understand why the protag needs so much money, his goal has never been changed since the start, its to travel to the great trade route to find his father, in other words you people seem to forgot how important money is in the world, he could dump his mother aside (who is 24-ish years old [she gave birth to the protag at around 16 years old] and took care of him and guiding him in the "feeling" of water system for 8-ish years as a single mother since during the time she got married to his father, 6 days after the marriage ceremony he left with his team to the great trade routes and has never returned nor even a letter sent) and hunt for magical equipment and artifacts himself which also will train his magic capacity and water system affinity however that means spending less time learning/reading books in the school's library or deciphering magic circles and runes (since he is poor and can't afford a wand to form and help hold the magical circle formation together with runes in it to cast water system type-weaved magic swamp before the formation dissipates he came up with his own method, than further improved on it but it also backfired later on because there is a reason why there are so many runes in place in the magic circle formation but he still continues to use his own method once he understood that).

Also that the current offensive water system magic-type skill he knows is water ball, which is basically like splashing a bucket of water on you, so no, he can't choose that route to dump his mother at his current magic capacity and water element affinity and also another important reason is because protag is a filial person.

Anyway its a lot of stuffs and the protag needs money, nothing is free, except its the internet, pretty much almost everything is free lol.