User blog comment:A certain someone/The ONE and ONLY FLAW of the Railgun Anime/@comment-24516349-20140327052551/@comment-5230978-20140327175150

''I search on google for the meaning of ecchi and I deduce that ecchi is actually a very mild hentai series and is used to refer to softcore or playful sexuality in contradistinction to the word 'hentai' which connotes perversion or fetishism. For ecchi, sexual themes are hinted at, and is considered a type of fan service that can be found in shonen seinen and harem anime.''

Not exactly. Even though that definition is more or less correct, the term ecchi widespread even to series were there are a lot of fanservice scenes devoid of sexaully suggetive elements (e.g. licking an ice-cream, eating a banana, cream or milk over a girl's face) or active and coscious attempts of seduction. The most common examples are scenes of underessing girls or naked girls (generally in changing room, in a bathroom, or in a spa), with convenient censorships that cover their nipples and the pube (if they aren't covered, they aren't usually drawn at all in ecchi series), scenes with a male character (generally the male protagonist) that accidentally sees the panties or the underwear of a girl, or her naked body, scenes where a male character accindentally ends up touching soft parts of a girl's body, and so on. In Index and, to a lesser extent, in Railgun, which lacks scenes with a male character for obvious reasons, such scenes are often seen, though for a comical use, so they are full-fledged ecchi series.

To aru just simply gives us scenes of misaka wearing shorts(boxers) under her skirt, I don't think that an ecchi anime will simply give us scenes of shorts(boxers) and is more likely to portray a female wearing something more daring.

I'm not talking only about Railgun anime, to be precise I'm not talking about it at all, because it is only an adaptation filled with cloverfield, so I don't give it so much importance. I'm talking about the original series, novels and mangas. The only part of Railgun anime I'm talking about are the canon filler arcs (Big Spider and Poltergeist) written by the novel and manga author. Also, if you saw only scenes about Mikoto's shorts, I have to assume that you didn't read Index novel or watched its anime series, because there are more than some panties scene in that series (Daihasei Festival arc is good example).

Although to aru indeed have some sensitive scenes, they did not focus on it

A series doesn't need to be focused on a genre to fall under its category. Just think about how the harem genre is used in Index. The romantic feelings and relationship are rarely developed in Index, aside some exceptions like Shiage x Takitsubo, Mikoto and, in OT, Itsuwa (maybe even Misaki and Index, in OT). Its main purpose is seemingly to add new members to the Kamijou Faction and its secondary fuction is to give some comic fanservice scenes. However, even if Index is not a series focused on the harem genre, harem elements are used enought to make it an harem series. For the same reason Index, and, to a lesser extent, Railgun are ecchi series.